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advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 1 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity g eneral d escription the sx8638 is an ultra low power, fully integrated 8 - channel solution for ca pacitive touch - buttons and slider with proximity detection applications. unlike many capacitive touch solutions, the sx8638 features dedicated capacitive sense inputs (that requires no external components) in addition to 8 general purpose i/o ports (gpio). each gpio is typically configured as led driver with independent pwm source for enhanced lighting control such as intensity and fading . the sx8638 includes a capacitive 10 bit adc analog interface with a utomatic compensation up to 100pf. the high resolution capacitive sensing supports a wide variety of touch pad size s and shape s and allows capacitive buttons to be created using thick overlay materials (up to 5m m) for an extremely robust and esd immune system design. the sx8638 incorporates a versatile firmware that was specially designed to simplify capacitive touch solution design and offers reduced time - to - market. integrated multi - time programmable memory pro vides the ultimate flexibilit y t o modify key firmware parameters (gain, threshold, scan period , auto offset compensation? ) in the field without the need for new firmware development. the sx8638 supports the 400 khz i2c serial bus data protocol and includ es a field programmable slave address. the tiny 4 mm x 4 mm footprint makes it an ideal solution for portable, battery powered applications where power and density are at a premium. t ypical a pplication circuit proximity sx8638 gnd gpio5 gpio4 gpio3 gpio2 gpio1 gnd gpio0 vana resetb gnd gpio7 vdig gpio6 cn cp vdd scl intb sda analog sensor interface micro processor ram rom nvm i2c gpio controller power management clock generation rc pwm led controller bottom plate host d1 d0 d2 d3 d4 d5 d6 d7 cap2 cap3 cap4 cap5 cap6 cap7 cap0 cap1 d0 d1 d2 d3 d4 d5 d6 d7 k ey p roduct f eatur es ? complete eight sensors capacitive touch controller for buttons and slider ? pre - configured for 2 b uttons and a slider ? 8 led d rivers with individual intensity, fading control and autolight mode ? 256 steps pwm linear and logarithmic control ? proximity s ensing up to several centimetres ? high resolution capacitive sensing ? u p to 100pf of offset capacitance compensation at f ul l s ensitivity ? c apable of sensing through overlay m aterials up to 5mm thick ? extremely low power optimized for portable application ? 8 ua (typ) in sleep m ode ? 80 ua (typ) in doze mode ( s cann ing period 195 ms) ? 175 ua (typ) in active m ode ( scann ing period 30 ms) ? programma ble s canning period from 15ms to 1 5 00ms ? auto offset compensation ? e liminates false triggers due to environmental f acto r s (temperature, h umidity) ? initiated on power - up and configurable i ntervals ? multi - time in - field programmable firmware parameters for ultimate flexibility ? on - chip user programmable memory for fast, self contained start -up ? "smart" wake - up sequence for ea sy activation from doze ? no external components per sensor input ? internal c lock r equires n o e xternal c omponents ? differential sensor sampling for reduced emi ? 400 khz fast - mode i2c interface with interrupt ? - 40c to +85c operation a pplications ? notebook/netboo k/portable/handheld computers ? cell phones, pdas ? consumer products, instrumentation, automotive ? mechanical button replacement o rdering i nformation part number temperature r ange package sx8638 i0 5 au ltrt 1 - 40c to +85c lead free mlpq - ut28 1 3000 units/r eel * this device is rohs/weee compliant and halogen f ree
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 2 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity table of contents g eneral d escription ................................................................ ................................ ........................ 1 t ypical a pplication circuit ................................................................ ............................................ 1 k ey p roduct f eatures ................................................................ ..................................................... 1 a pplications ................................ ................................ ....................................................................... 1 o rdering i nformation ................................................................ ...................................................... 1 1 g eneral d escription ................................................................ ............................................... 4 1.1 pin diagram 4 1.2 marking information 4 1.3 pin description 5 1.4 simplified block diagram 6 1.5 acronym s 6 2 e lectrical c haracteristics ................................ ................................ ................................. 7 2.1 absolute maximum ratings 7 2.2 recommended operating conditions 7 2.3 thermal characteristics 7 2.4 electrical specifications 8 3 f unctional descriptio n ................................................................ ........................................ 10 3.1 quickstart application 10 3.2 introduction 10 3.2.1 general 10 3.2.2 gpios 11 3.2.3 parameters 11 3.2.4 configuration 11 3.3 scan period 12 3.4 operation modes 12 3.5 sensors on the pcb 14 3.6 button and slider information 15 3.6.1 button informatio n 15 3.6.2 slider information 15 3.7 analog sensing interface 17 3.8 offset compensation 18 3.9 processing 19 3.10 configuration 1 9 3.11 power management 21 3.12 clock circuitry 21 3.13 i2c interface 21 3.14 reset 22 3.14.1 power up 22 3.14.2 resetb 22 3.1 4.3 software reset 23 3.15 interrupt 24 3.15.1 power up 24 3.15. 2 assertion 24 3.15.3 clearing 24
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 3 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.15.4 example 25 3.16 general purpose input and outputs 25 3.16.1 introduction and definitions 25 3.16.2 gpi 26 3.16.3 gpp 26 3.16.4 gpo 27 3.16.5 intensity index vs pwm pulse width 30 3.17 smart wake up 31 4 p in descriptions ................................ ................................ ..................................................... 32 4.1 introduction 32 4.2 asi pins 32 4.3 host interface pins 33 4.4 power management pins 36 4.5 general purpose io pins 37 5 d etailed c onfiguration descrip tions ................................ ................................ .............. 38 5.1 introduction 38 5.2 general parameters 41 5.3 capacitive sensors parameters 42 5 .4 button parameters 47 5.5 slider parameters 51 5.6 mapping parameters 55 5.7 gpio parameters 58 6 i2c i nterface ................................................................ ........................................................... 62 6.1 i2c write 62 6.2 i2c read 63 6.3 i2c registers overview 64 6.4 status registers 65 6.5 control registers 68 6.6 spm gateway registers 70 6.6.1 spm write sequence 71 6.6.2 spm read sequence 72 6.7 nvm burn 73 6.8 monitor mode 74 7 a pplication i nformation ................................ ................................ ...................................... 75 7.1 typical application schematic 75 7.2 example of touch+proximity mo dule 76 7.2.1 overview 76 7.2.2 operation 76 7.2.3 performance 76 7.2.4 schematics 77 7.2.5 layout 78 8 r eferences ................................ ................................ ................................ ............................. 79 9 p ackaging i nformation ................................ ................................ ................................ ........ 80 9.1 package outline drawing 80 9.2 land pattern 80
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 4 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 1 g eneral d escription 1.1 pin diagram sx 8638 top view 1 2 3 4 5 6 7 21 20 19 18 17 16 15 8 9 10 11 12 13 14 22 23 24 25 26 27 28 bottom ground pad cap2 cap3 cap4 cap5 cap6 cap7 gnd gpio5 gpio4 gpio3 gpio2 gpio1 gnd gpio0 cap1 cap0 vana resetb gnd gpio7 vdig gpio6 cn cp vdd scl intb sda figure 1 pinout diagram 1.2 marking information fn28 yyww xxxxx r05 yyww = date code xxxxx = semtech lot number r05 = semtech code figure 2 marking information
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 5 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 1.3 pin description number name type description 1 cap1 a nalog capacitive sensor 1 2 cap2 a nalog capacitive sensor 2 3 cap3 a nalog capacitive sensor 3 4 cap4 a nalog capacitive sensor 4 5 cap5 a nalog capacitive sensor 5 6 cap6 a nalog capacitive sensor 6 7 cap7 a nalog capacitive sensor 7 8 cn analog integration c apacitor , negative terminal (1nf between cn and cp) 9 cp analog integration c apacitor , p ositive terminal (1nf between cn and cp) 10 vdd power m ain input power supply 11 intb digital o utput int errupt , active low , requires pull up resistor (on host or external) 12 scl digital input i2c clock, requires pull up resistor (on host or external) 13 sda digital input/output i2c data , requires pull up resistor (o n host or external) 14 gpio0 digital in put/output general purpose input/output 0 15 gpio1 digital input/output general purpose input/output 1 16 gnd g round g round 17 gpio2 digital input/output general purpose input/output 2 18 gpio3 digital input/output general purpose input/output 3 19 gp io4 digital input/output general purpose input/output 4 20 gpio5 digital input/output general purpose input/output 5 21 gnd ground g round 22 gpio6 digital input/output general purpose input/output 6 23 gpio7 digital input/output general purpose input/o utput 7 24 vdig analog digital core decoupling , connect to a 100nf decoupling capacitor 25 gnd ground g round 26 resetb digital i nput active low reset. connect to vdd if not used. 27 vana analog analog core decoupling , connect to a 100nf decoupling capa citor 28 cap0 a nalog capacitive sensor 0 bottom plate gnd ground exposed pad connect to ground table 1 pin description
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 6 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 1.4 simplified block diagram the simplified block diagram of the sx8638 is illustrated in figure 3 . sx8638 cap2 cap3 cap4 cap5 cap6 cap7 gnd gpo5 gpo4 gpo3 gpo2 gpo1 gnd gpo0 vana resetb gnd gpo7 vdig gpo6 cn cp vdd scl intb sda analog sensor interface micro processor ram rom nvm i2c gpio controller power management clock generation rc pwm led controller bottom plate cap0 cap1 figure 3 simplified block diagram of the sx8638 1.5 acronyms asi analog sensor interface dcv digital compensation v alue gpi general purpose input gpo general purpose output gpp ge neral purpose pwm mtp multiple time programmable nvm non volatile memory pwm pulse width modulat ion qsm quick start memory spm shadow parameter memory
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 7 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 2 e lectrical c haracteristics 2.1 absolute maximum ratings stresses above the values listed in ?absolute maximum ratings? may cause permanent damage to the device. this is a stress rating only and functional operation of the device at these, or any other conditions beyond the ?recommended operating conditions?, is not implied. exposure to absolute maximum ra ting conditions for extended periods may affect device reliability . parameter symbol min. max. unit supply voltage vdd - 0.5 3.9 v input voltage (non - supply pins) v in - 0.5 3.9 v input current (non - supply pins) i in 10 ma operating junction temperature t jct 125 c reflow temperature t re 260 c storage temperature t stor - 50 150 c esd hbm (human body model) (i) esd hbm 3 kv latchup (ii) i lu 100 ma table 2 absolute maximum ratings (i) tested to jedec standard jesd22 - a114 (i i) tested to jedec standard jesd78 2.2 recommended operating conditions parameter symbol min. max . unit supply voltage vdd 2.7v 3.6 v supply voltage dro p (ii i , iv , v ) vdd dr op 100 m v supply voltage for nvm programming vdd 3.6 3.7 v ambient temperature rang e t a - 40 85 c table 3 recommended operating conditions (iii) performance for 2.6v < vdd < 2.7v might be degraded. (iv ) operation is not guaranteed below 2.6v. s hould vdd briefly drop below this minimum value, then the sx8638 may r equire; - a hardware reset issued by the host using the resetb pin - a software reset issued by the host using the i2c interface ( v) in the event the host processor is reset or undergoes a power off/on cycle, it is recommended that the host also resets the sx8638 and assures that parameters are re - written into the spm (should these differ to the parameters held in nvm). 2.3 thermal characteristics parameter symbol min. max . unit thermal resistance - junction to ambient ( v i ) ja 25 c/w table 4 thermal characteristics ( v i ) static airflow
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 8 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 2.4 electrical specifications all values are valid within the operating conditions unless otherwise specified. parameter symbol conditions min. typ . max . unit current consumption active mode , average i op,active 30 ms scan period , 8 sensors enabled, minimum sensitivity 175 225 ua doze mode , average i op, doze 195 ms scan period , 8 sens ors enabled , minimum sensitivity 80 1 1 0 ua sleep i op,sleep i2c and gpi listening, sensors disabled 8 17 ua gpio, set as input, r eset b, scl, sda input logic high v ih 0.7* vdd vdd + 0.3v v input logic low v il vss applied to gnd pins vss - 0.3v 0.8 v input leakage current l i cmos input 1 ua pull up resistor r pu when enabled 660 k ? pull down resistor r pd when enabled 660 k ? gpio set as output , int b, sda output logic high v oh i oh <4ma vdd - 0.4 v output logic low v ol i ol,gpio <12ma i ol,sda,intb <4ma 0.4 v start - up p ower up time t por time between risin g edge vdd and rising i ntb 150 ms resetb pulse w idth t res 50 n s recommended external components c apacitor between vdig, gnd c vdig type 0402, tolerance +/ - 50% 100 nf c apacitor between vana, gnd c vana type 0402, tolerance +/ - 50% 100 nf c apacitor between cp, cn c int type 0402, cog, tolerance +/ - 5 % 1 nf c apacitor between vdd , gnd c vdd type 0402, tolerance +/ - 50% 270 nf table 5 electrical specifications
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 9 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity parameter symbol conditions min. typ . max . unit i2c t iming s pecifications (i) scl clo ck frequency f scl 400 khz scl low period t low 1.3 us scl high period t high 0.6 us data setup time t su;dat 100 ns data hold time t hd;dat 0 ns repeated start setup time t su;sta 0.6 us start condition hold time t hd;sta 0.6 us stop condition setup time t su;sto 0.6 us bus free time between stop and start t buf 500 us input glitch suppression t sp 50 ns table 6 i2c timing specification notes: (i) all timing specifications , fi gure 4 and figure 5 , refer to voltage levels (v il , v ih , v ol ) defined in table 5 . the interface complies with slave f/s mode as described by nxp: ?i2c - bus specification, rev. 03 - 19 june 2007? sda scl t su;sta t hd;sta t su;sto t buf 70% 30% 70% figure 4 i2c start and stop timing sda scl t low t high t hd ; dat t su ; dat t sp 70 % 30 % 70 % 30 % figure 5 i2c data timing
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 10 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3 f unctional descriptio n 3.1 quickstart application t he sx8638 is pre configured (quickstart applic ation) for an application with 2 buttons, a slider (consisting of 6 sensors) and 8 led drivers using logarithmic pwm fading. implementing a schematic based on figure 6 will be immediately operational after powering without program ming the sx8638 (even without host). host sx8638 gnd gpio 5 gpio 4 gpio3 gpio2 gpio1 gnd gpio0 vana resetb gnd gpio7 vdig gpio6 cn cp vdd scl intb sda analog sensor interface micro processor ram rom nvm i 2 c gpio controller power management clock generation rc pwm led controller bottom plate d 1 d 0 d 2 d 3 d 4 d 5 d 6 d 7 cap 2 cap 3 cap 4 cap 5 cap 6 cap 7 cap 0 cap 1 d 0 d 1 d 2 d 3 d 4 d 5 d 6 d 7 figure 6 quickstart a pplication touching the sensor on the cap0 pin will enable automatically the led connected to gpio0. when the cap0 sensor is released the led on gpio0 will slowly fade - out using smooth logarithmic fading. the sensor cap1 has its led associated on pin gpio1 showing a touch or a release. the sensors on cap2 to cap7 are used in a slider configuration. a finger on the slider will enable the led on gpio2 to gpio7 indicating the finger slider position. the sensor detection and the led fading described above are operational without any host interaction. this is made possible using the sx8638 autolight feature described in the following sections. 3.2 i nt roduction 3.2.1 general the sx8638 is intended to be used in applications which require capacitive sensors covered by isolating overlay material and which need to detect the proximity of a finger/hand though the air. a finger approaching the capacitive sensors will change the charge that can be loaded on the sensors. the sx8638 measures the change of charge and conver ts that into digital value s (ticks). the larger the charge on the sensors, the larger the number of ticks will be. the charge to ticks conversion i s done by the sx8638 analog sensor interface (a si ). the ticks are further processed by the sx8638 and converted in a high level, easy to use information for the user?s host.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 11 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity the information between sx8638 and the user?s host is passed through the i2c inter face with an additional interrupt signal indicating that the sx8638 has new information. for buttons this information is simply touched or released. 3.2.2 gpios a second path of feedback to the user is using general purpose input output (gpio) pins. the sx8638 offers eight individual configurable gpio pins. the gpio can e.g. b e set as a led driver which slowly fade - in when a finger touches a button and slowly fade - out when the button is released . fading intensity variations can be logarithmic or linear. interval speed and initial and final light intensity can be selected by the user. the fading is do ne using a 256 steps pwm. the sx8638 has eight individual pwm generators, one for each gpio pin. the led fading can be initiated automatically by the sx8638 by settin g the sx8638 autolight feature. a simple touch on a sensor and the corresponding led will fade - in without any host interaction over the i2c. in case the autolight featu re is disabled then the host will decide to start a led fading - in period, simply by sett ing the gp 0 pin to ?high? using one i2c command. the sx8638 will then slowly fade - in the led using the pwm autonomously. in case the host needs to have full control of the led intensity then the host can set the gpio in gpp mode. the host is then able to s et the pwm pulse width freely at the expense of an increased i2c occupation. the gpios can be set further in the digital standard input mode (gpi). 3.2.3 parameters the sx8638 has many low level built - in, fixed algorithms and procedures. to allow a lot of freed om for the user and adapt the sx8638 for different applications these algorithms and procedures can be configured with a large set of parameters which will be described in the following sections. examples of parameters are which sensors are buttons or whic h sensors are parts of a slider , which gpio is used for out puts or leds and which gpio is mapped to which button. sensitivity and detection thresholds of the sensors are part of these parameters. assuming that overlay material and sensors areas are identic al then the sensitivities and thresholds will be the same for each sensor. in case sensors are not of the same size then sensitivities or thresholds might be chosen individually per sensor. so a smaller size sensor can have a larger sensitivity while a big size sensor may have the lower sensitivity. 3.2.4 configuration during a development phase the parameters can be determined and fine tuned by the users and dow n l o a ded over the i2c in a dynamic way. the parameter set can be downloaded over the i2c by the host each time the sx8638 boots up. this allows a flexible way of setting the parameters at the expense of i2c occupation. in case the parameters are frozen they can be programmed in multiple time programmable (mtp) non volatile memory ( nvm) on the sx8638 . the programmi ng needs to be done once ( over the i2c). the sx8638 will then boot up from the nvm and additional parameters from the host are not required anymore. in case the host desir es to overwrite the boot - up nvm parameters (partly or even complete) this ca n be done by additional i2c communications.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 12 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.3 scan period the basic operation scan period of the sx8638 sensing interface can be split into three periods over time. in the first period (sensing) the sx8638 is sensing all enabled cap inputs , from cap0 tow ards cap7 . in the second period (processing) the sx8638 processes the sensor data, verifies and updates the gpio and i2c status registers . in the third period (timer) the sx8638 is set in a low power m ode and waits until a new cycle starts. figure 7 shows the different sx8638 periods over time. cap 0 cap1 cap7 sensing data processing processing timer cap0 cap1 scan period time timer figure 7 scan period the scan period determines the minimum reaction time of the sx8638 . the scan period can be configured by the h ost from 15ms to values larger than a second. the reaction time is defined as the interval between a touch on the sensor and the moment that th e sx8638 generates the interrupt on the intb pin . the shorter the scan period the faster the reaction time will b e. very low power consumption can be obtained by setting very lo ng scan periods with the expense of having longer reaction times. important: all external events like gpio, i2c and intb are updated in the processing period, so once every scan period. if e. g. a gpi would change state directly after the processing period then this will be reported with a delay of one scan period later in time. 3.4 operation modes the sx8638 has 3 operation modes. the main difference is found in the reaction time (corres ponding to the scan period ) and power consumption. active mode offers fast scan period s . the typical reaction time is 30ms. a ll enabled sensors are scanned and information data is processed within this interval. doze mode increases the scan period time which in creases the reaction time to 195 ms typical and at the same time reduces the operating current. sleep mode turns the sx8638 off , except for the i2c and gpi peripheral, minimizing operating current while maintaining the power supplies. in sleep mode the sx8 638 does not do any sensor scanning. the user can specify other scan periods for the active and doze mode and decide for other compromises between reaction time and power consumption. in most applications the reaction time needs to be fast when fingers are present, but can be slow when no person uses the application. in case the sx8638 is not used for a specific time it can go from active mode into doze mode and power will be saved . this time - out is dete rmined by the passive timer which can be configured by the user or turned off if not re q uired.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 13 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity to leave doze mode and enter active mode this can be done by a simple touch on any button. for some applications a single button touc h might cause undesired wakening up and active mode would be entered too often . the sx8638 offers therefore a smart wake - up sequence feature in which the user need s to touch and release a correct sequence of buttons before active mode will be entered. this is explained in more detail in the wake - up sequence section. the host can d ec ide to force the operating mode by issuing commands over the i2c (using register compopmode ) and take fully control of the sx8638 . the diagram in figure 8 shows the available operation modes and the possible transitions. active mode doze mode sleep mode wake - up sequence detected or gpi interrupt or i 2 c cmd gpi interrupt or i 2 c cmd i 2 c cmd i 2 c cmd i2c cmd power on i2c cmd passive timeout 'i2c cmd' - write to compopmode[1:0] figure 8 operation modes
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 14 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.5 sensors on the pcb the capacitive sensors are relatively simple copper areas on the pcb connected to the eight sx8638 c apacitive sensor input pins (cap 0? cap7 ).the sensors are cove red by isolating overlay material (typically 1mm...3mm) . the area of a sensor is typically one square centimeter which corresponds about to the area of a finger touching the overlay material. the capacitive sensors can be setup as on/off buttons for either touch or proximity sensing (see example figure 9 ) or arranged in a slider configuration ( see example figure 10) for e.g. menu scrolling or volume control applications. figure 9 pcb top layer of three touch buttons sensors surrounded by a proximity sensor figure 10 pcb top layer of one slider using six sensors (surrounded by ground plane) please refer to the layout guidelines application note [1], fo r more details.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 15 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.6 button and slider information 3.6.1 button information the touch buttons have two simple states (see figure 11 ): on (touched by finger) and off (released and no finger press). off on off off figure 11 b uttons a finger is detected as soon as the number of ticks from the asi reaches a user - defined threshold plus a hysteresis. a release is detected if the tick s from the asi go below the threshold minus a hysteresis . the hysteresis around the threshold avoids rapid touch and rele ase signaling during transients. buttons can also be used to do proximity sensing. the principle of proximity sensing operation is exactly the same as for touch buttons except that proximity sensing is done s everal centimeters above the overlay through the air. on state means that finger/hand is detected by the sensor and off state means the finger/hand is far from the sensor. 3.6.2 slider information in case sensors are arranged in a slider configuration the on, o ff information remains available as if it would be a single sensor button. on off figure 12 slider o n , off wherever the slider is touched the information will be set to on. if no finger is present the slider information will be off. due to the 2 dimensional character of the slider more information can be derived by processing the ticks. during a touch a finger will influence most of the time the charge on one or two sensors but never all of the sensors at th e same time. some sensor ticks will be lar ger than others based on the finger position. the processing algorithms can therefore determine where the finger is positioned on the slider . interpolation between sensors increases the resolution beyond the number of sensors in the slider . the interpolation can be done already on the pcb sensor structures (analog , like the chevron slider in figure 10) and as well by sx8638 digital processing of the ticks using cent er of gravity calculation s. t he position of the finger on the pcb structures var ies between the minimum zero and a user defined max imum ( figure 13 ).
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 16 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity ....x... position min max figure 13 slider p osition the position belonging t o the minimum and associated to a sensor is defined arbitr arily . the sx8638 defines the minimum position to the sensor with the lowest cap pin index. e.g . if cap0 is a button (or disabled) and cap1 to cap7 are the sensors of the slider then the position ? z ero ? starts at cap1 and the maximum is found at cap7 . in addition to the slider position, the sx8638 allows to detect finger movements . the movement occurs if the finger position changes a certain step size between t w o succeeding scan period s . a very slow moving finger will not be considered as a mov e ment as the changing position will be minor. the sx8638 allows detecting a move low (direction max to min) (see figure 14 ) a nd a move high (direction min to max) (see figure 15). min max figure 14 slider move low min max figure 15 slider move high
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 17 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.7 analog sensing interface the analog sensing interface (asi) convert s the charge on the sensors into ticks which will be further digitally processed. the basic principle of the asi will be explained in this section. the asi consists of a multiplexer selecting the sensor, analog switches, a reference voltage, a n adc sigma delta converter , an offset compensation dac and an externa l integration capacitor (see figure 16 ). switches cap2 cap1 cap0 cn cp analog multi- plexor offset compensation dac adc ticks (raw) compensation dcv asi processing cint voltage reference low pass ticks-diff ticks-ave cap7 figure 16 analog sensor interface to get the ticks repres enting the charge o n a specific sensor the asi w ill execute several steps. the charge on a sensor cap (e.g . cap0) will be accumulated multiple times on the external integration capacitor, cint . this results in an increasing voltage on cint proportional to the capacitance on cap0. at this stage the offset compensation dac is enabled. the compensation dac generates a voltage proportional to an estimation of the external capacitance. the estimation is obtained by the offset compensation procedure executed e.g. at power - up. the d ifference between the dac output and the charge on cint is the desired signal. in the ideal case the difference of charge will be converted to zero ticks if no finger is present and the number of ticks becomes high in case a finger is present. the differen ce of charge on cint and the dac output will be transferred to the adc (sigma delta integrator). after the charge trans fer to the adc the steps above will be repeated. the larger the number the cycles are repeated the larger the signal out of the adc with improved snr . the sensitivity is therefore directly related to the number of cycles. the sx8638 allows setting the sensitivity for each sensor individually in applications which have a variety of sensors sizes or different overlays or for fine - tuning perf ormances. the optimal sensitivity is depending heavily on the final application. if the sensitivity is too low the ticks will not pass the thresholds and touch/proximity detection will not be possible. in case the sensitivity is set too large, some power w ill be wasted and false touch/proximity information may be output (ie for touch buttons => finger not touching yet, for proximity sensors => finger/hand not close enough). once the asi has finished the first sensor , the ticks are stored and the asi will s tart measu ring the next sensor until all (enabled) sensors pins have been treated. in case some sensors are disab led then these result in lower power consumption simply because the asi is active for a shorter period and the following processin g period will be shorter .
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 18 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity the ticks from the asi will then be handled by the digital processing. 3.8 offset compensation the capacitance at the cap pins is determined by an intrinsic capacitance of the integrated circuit, the pcb traces , ground coupling and the sensor p lanes. this capacitance is relatively large an d might become easily some ten s of p f . this parasitic capacitance will vary only slowly over time due to environmental changes. a finger touch is in the order of one pf . if t he finger approaches the sensor this occurs typically fast. the asi has the difficult task to detect and distinguish a small, fast changing capacitance, from a large, slow varying capacitance. this would require a very precise, high resolution adc and complicated, power consuming, digital pr ocessing. the sx8638 features a 16 bit dac which compensates for the large, slow varying capacitance already in front of the adc. in other words the adc converts only the desired small signal. in the ideal world the adc will put out zero ticks even if the external capacitance is as high as 100pf. at e ach power - up of the sx8638 the digital compensation v alues (dcv) are estimated by the digital processing algorithms. the algorithm will adjust the compensation values such that zero ticks will be generated by the adc. once the correct compensation values are found these will be stored and used to compensate each cap pin. if the sx8638 is shut down the compensation values will be lost. at a next power - up the procedure starts all over again. this assures that th e sx8638 will operate under any condition. powering up at e.g. different temperatures will not change the performance of the sx8638 and the host does not have to do anything special. the dcvs do not need to be updated if the external conditions remain stab le. however if e.g. temperature changes this will influence the external capacitance. the adc ticks will drift then slowly around zero values basically because of the mismatch of the compensation circuitry and the external capacitance. in case the average value of the ticks become higher than the positive noise threshold (configurable by user) or lower than the negative threshold (configurable by user) then the sx8638 will initiate a compensation procedure and find a new set of dcvs. compensation procedur es can as well be initiated by the sx8638 on periodic intervals. even if the ticks remain within the positive and negative noise thresholds the compensation procedure will then estimate new sets of dcvs. finally the host can initiate a compensation proced ure by using the i2c interface (in active or doze mode) . this is e.g. required after the host changed the sensitivity of sensors.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 19 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.9 processing the first processing step of the raw ticks, coming out of the asi, is low pass filtering to obtain an estimation o f the average capacitance: tick - ave (see figure 17). this slowly varying average is important in the detection of slowly changing environmental changes. ticks (raw) compensation dcv asi processing low pass tick-diff tick-ave processing gpio controller pwm led controller i2c spm figure 17 processin g the difference of the tick average and the raw ticks, tick - diff, is a good estimation of rapid changing input capacitances. the tick - diff, tick - ave and the configuration parameters in the spm are then processed and determines the sensor information, i2 c registers status and pwm control. 3.10 configuration figure 18 shows the building blocks used for configuring the sx8638 . micro processor mtp nvm i 2c sx8638 host spm qsm figure 18 configuration the default configuration pa rameters of the sx8638 are stored in the quick start memory (qsm) . this configuration data is setup to a very common application for the sx8638 with buttons and a slider . without any programming or host interaction the sx8638 will startup in the quick star t application.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 20 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity the qsm settings are fixed and can not be changed by the user. in case the applica tion needs different settings than the qsm settings then the sx8638 can be setup and/ or programmed over the i2c interface. the configuration parameters of the sx8638 can be stored in the multiple time programmable (mtp) non volatile memory ( nvm). the nvm contains all those parameters that are defined and stable for the application. examples are the number of sensors enabled, sensitivity, active and doze scan pe riod. the details of these parameters are described in the next chapters. at power up the sx8638 checks if the nvm contains valid data. in that case the configuration p arameter source becomes the nvm. if the nvm is empty or non - valid then the configuratio n source becomes the qsm. in the next step the sx8638 copies the configuration parameter source (qsm or nvm) into the shadow parameter m emory (spm). the sx8638 is operational and uses the configuration parameters of the spm. during power down or reset eve nt the spm loses all content. it will automatically be reloaded (from qsm or nvm) following power up or at the end of the reset event. the host will interface with the sx8638 through the i2c bus. the i2c of the sx8638 consists of 16 registers. some of the se i2c registers are used to read the status and information of the button and the slider . other i2c registers allow the host to take control of the sx8638 . the host can e.g. decide to change the operation mode from a ctive mode to doze mode or go into s lee p (according to figure 8 ). two additional mode s allow the host to have an access to the sp m or indirect access to the nvm. these modes are required during development, can be used in real time or in - field programming. figure 19 shows the host spm mode. in this mode the host can decide to overwrite the spm. this is useful during the development phases of the application where the configuration parameters are not yet fully defined and as well during the op eration of the application if some parameters need to be changed dynamically. micro processor mtp nvm i 2 c sx8638 host spm figure 19 host spm mode the content of the spm remains valid as long as the sx8638 is powered and no reset is performed . af ter a power down or reset the host needs to re - write the spm if relevant for the application. figure 20 shows the host nvm mode. in this m ode the host wil l be able to write the nvm.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 21 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity micro processor mtp nvm i 2c sx8638 host spm 1 2 figure 20 host nvm mode the writ ing of the host towards the nvm is not done directly but done in 2 steps ( figure 20 ). in the first step the host writes to the spm (as in figure 19 ). in the second step the host signals the sx8638 to co py the spm content into the nvm. initially the nvm memory is empty and it is required to determine a valid parameter set for the application. this can be done during the development phase using dedicated evaluation ha rdware representing the final application. this development phase uses probably initially the host spm mode which allows faster iterations. once the parameter set is determined this can be written to the nvm over the i2c using the 2 steps approach by the h ost or a dedicat ed programm er for large volumes production (as described in the paragraphs 6.6 and 6.7 ). 3.11 power management the sx8638 uses on - chip voltage regulators which are controlled by the on - chip microprocessor. the regulators need to be stabilized with an external capacitor between vana and ground and be tween vdig and ground (see table 5 ) . both regulators are designed to only drive the sx8638 internal circuitry and must not be loaded externally. 3.12 clock c ircuitry the sx8638 has its own internal clock generation circuitry that doe s not require any external components. the clock circuitry is optimized for low power operation and is controlled by the on - chip microprocessor. the typical operating frequency of the oscillating core is 16 .7 mhz from which all other lower frequencies are d erived. 3.13 i2c interface the i2c interface allows the communication between the host and the sx8638 . the i2c slave implemented on the sx8638 is compliant with the standard (100kb/s) and fast mode (400kb/s) t he default sx8638 i2c address equals 0b010 1011. a different i2c address can be pr ogrammed by the user in the nvm.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 22 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.14 reset the reset can be performed by 3 sources: - power up, - resetb pin, - software reset. 3.14.1 power up during power up the intb is kept low. once the power up sequence is terminated the in tb is released autonomously. the sx8638 is then ready for operation. vdd intb time vdd t por supply voltage vddmin time sx 8638 ready figure 21 power up vs. intb during the power on period the sx8638 stabilizes the internal regulators, rc clocks and the firmware initializes all registers. during the power up the sx8638 is not accessible and i2c communications are forbidden. as soon as the intb rises the sx8638 will be ready for i2c communication. 3.14.2 resetb when resetb is driven low the sx8638 will reset and start th e power up sequence as soon as resetb is driven high or pulled high. in case the user does not require a hardware reset control pin then the resetb pin can be connected to vdd. vdd t res resetb time sx8638 startup vdd intb time t por sx8638 ready figure 22 hardware r es et
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 23 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.14.3 s oftware r eset to perform a software reset the host needs to write 0xde followed by 0x00 at the softreset register at address 0xb1. softreset register time sx8638 startup vdd intb time t por sx8638 ready 0xde 0x00 figure 23 software r eset
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 24 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.15 interrupt 3.15.1 power up during power up t he intb is kept low. once the power up sequence is terminated the intb is released autonomously. the sx8638 is then ready for operation. vdd intb time vdd t por supply voltage vddmin time sx8638 ready figure 24 power up vs. intb during the power on period the sx 8638 stabilizes the internal regulators, rc clocks and the firmware initializes all registers. during the power up the sx8638 is not accessible and i2c communications are forbidden. as soon as the intb rises the sx8638 will be ready for i2c communication. 3.15.2 assertion intb is updated in active or doze mode once every scan period. the intb will be asserted : at the following events: ? if a button event occurred (touch or release if enabled). i2c registers capstatmsb and capstatlsb show the detailed status of th e buttons , ? if a slider event occurred (touch, release, move high, move low or position change). i2c registers capstatmsb, sldposmsb and sldposlsb show the detailed status of the slider , ? if a gpi edge occurred (rising or falling if enabled) . i2c register gp istat shows the detailed status of the gpi pins , ? when actually entering active or doze mode either through automatic wakeup or via host request (may be delayed by 1 scan period). i2 c register compopmode shows the current operation mode , ? once compensation procedure is completed either through automatic trigger or via host request (may be delayed by 1 scan period) , ? once spm write is effective (may be delayed by 1 scan period) , ? once nvm burn procedure is completed (m ay be delayed by 1 scan period), ? during res et (power up, hardware resetb, software reset). 3.15.3 clearing intb is updated in active or doze mode once every scan period. the clearing of the intb is done as soon as the host per forms a read to the irqsrc i2c register or reset is completed
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 25 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.15.4 example a typi cal example of the assertion and clearing of the intb and the i2c communication is shown in figure 25 . off on on off intb time i2c 1 2 3 4 read read figure 25 interrupt and i2c when a button is touched the sx8638 will as sert the interrupt ( 1). the host will read the irqsrc information over the i2c and this clears the interrupt (2) . if the finger releases the button the interrupt will be asserte d (3). the host reading the irqsrc information will clear the interrupt (4). i n case the host does not react to an interrupt this results in a missing touch. 3.16 general purpose input and outputs 3.16.1 introduction and definitions the sx8638 offers eight general purpose input and outputs (gpio) pins which can be configured in any of these mo des: - gpi (general purpose input) - gpp (general purpose pwm) - gpo (general purpose output) each of these modes is described in more details in the following sections. the polarity of the gpp and gpo pins is defined as in figure below, driving an led as example. it has to be set accordingly in spm parameter gpiopolarity. gpio gpio vdd ( a) (b) figure 26 polarity definition, (a) normal, (b) inverted
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 26 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity the pwm blocks used in gpp and gpo modes are 8 - bits based and clocked at 2 mhz typ. hence offering 256 selectable pulse width values with a granularity of 128us typ. time vdd (a) period width time vdd (b) period width figure 27 pwm definition, (a) small pulse width, (b) large pulse width 3.16.2 gpi gpios configured as gpi will oper ate as digital inputs with standard low and high logic levels. optional pull - up/down and debounce can be enabled. each gpi is individually edge programmable for intb generation which will also exit sleep/doze mode if relevant. spm/i2c parameters applicab le in gpi mode are listed in table below. please refer to the relevant spm/i2c parameters sections for more details. gpi spm gpiomode x gpiopullupdown x gpiointerrupt x gpio debounce x i2c irqsrc[4] x gpistat x table 7 spm/i2c parameters applicable in gpi mode 3.16.3 gpp gpios configured as gpp will operate as pwm outputs directly controlled by the host. a typical application is led dimming. typical gpp operation is illustrated in figure below. i 2c 0% 50% 100% sx8638 host sx8638 host gppintensity = 0x7f i2c gppintensity = 0xff figure 28 led control in gpp mode spm/i2c parameters applicable in gpp mode are listed in table below. please refer to the relevant spm/i2c parameters sections for more details.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 27 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity gpp spm gpiomode x gpiooutpwrup x 1 gpio p olarity x gpiointensityon x 1 gpiointensityoff x 1 gpiofunction x i2c gpppinid x gppintensity x 1 1 at power up, gpp intensity of each gpp pin is initialized with gpiointensity on or gpio intensityoff depending on gpiooutpwrup corresponding bits value . table 8 spm/i2c parameters applicable in gpp mode 3.16.4 gpo gpios configured as gpo will operate as digital outputs which can generate both standard low/high logic levels and pwm low/high duty cycles levels. typical application is led on/off control. transitions between on and off states can be triggered either automatically in autolight mode or manually by the host. this is illustrated in figures below. i 2 c off on off sx8638 host sx8638 host gpoctrl = 1 i2c gpoctrl = 0 figure 29 led control in gp o mode, autolight off off on off figure 30 led control in gpo mode, autolight on (mapped to button) additionally these transitions can be configured to be done with or without fading following a logarithmic or li near function. this is illustrated in figures below. time pwm pulse width intensity on intensity off fading steps inc . time time intensity on intensity off fading steps inc. time (a) (b) trigger trigger pwm pulse width figure 31 gpo on transition (led fade in), normal polarity, (a) linear, (b) logarithmic
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 28 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity time intensity on intensity off fading steps inc. time time intensity on intensity off fading steps inc. time (a) (b) trigger trigger pwm pulse width pwm pulse width figure 32 gpo on transition (led fade in), inverted polarity, (a) linear, (b) logarithmic the fading out (e.g. after a button is released) is identical to the fading in but an additional off delay can be added before the fading starts ( figure 33 and figure 34 ). intensity off intensity on fading steps dec . time trigger time time intensity off intensity on fading steps ( b ) trigger off delay dec . time off delay pwm pulse width pwm pulse width figure 33 gpo off transition (led fade out), normal polarity, (a) linear, (b) logarithmic time intensity off intensity on fading steps dec. time (a) trigger time intensity off intensity on fading steps dec. time (b) trigger off delay off delay pwm pulse width pwm pulse width figure 34 gpo off transition (led fade out), inverted polarity, (a) linear, (b) logarithmic please note that standard high/low logic signals are just a specific case of gpo mode and can also be generated simply by setting inc/dec time to 0 (ie off ) and programming intensity off/on to 0x00 and 0xff.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 29 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity spm/i2c parameters applicable in gpo mode are listed in table below. gpo spm gpiomode x gpiooutpwrup x 1 gpio autoligth x gpio polarity x gpiointensityon x gpiointensityoff x gpiofunction x gpioincfactor x gpiodecfactor x gpioinctime x gpiodectime x gpiooffdelay x i2c gpoctrl x 2 1 only if autolight is off, else must be left to 0 (default value) 2 only if autolight is off, else ignored table 9 spm/i2c pa rameters applicable in gpo mode
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 30 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.16.5 intensity index vs pwm pulse width tables below are used to convert all intensity indexes parameters gpio intensityoff , gpiointensity on and gppintensity but also to generate fading in gpo mode during fading in(out), the index is automatically incremented(decremented) at every inc(dec)time x inc(dec)factor until it reaches the programmed gpiointensity on ( off ) value. index lin/log index lin/log index lin/log index lin/log index lin/log index lin/log index lin/log index lin /log 0 0/ 0 32 33/ 5 64 65/ 12 96 97/ 26 128 129/ 48 160 161/ 81 192 193/ 125 224 225/ 184 1 2/ 0 33 34/ 5 65 66/ 13 97 98/ 27 129 130/ 49 161 162/ 82 193 194/ 127 225 226/ 186 2 3/ 0 34 35/ 5 66 67/ 13 98 99/ 27 130 131/ 50 162 163/ 83 194 195/ 129 226 227/ 188 3 4/ 0 35 36/ 5 67 68/ 13 99 100/ 28 131 132/ 51 163 164/ 84 195 196/ 130 227 228/ 190 4 5/ 0 36 37/ 5 68 69/ 14 100 101/2 9 132 133/ 52 164 165/ 86 196 197/ 132 228 229/ 192 5 6/ 2 37 38/ 6 69 70/ 14 101 102/2 9 133 134/ 53 165 166/ 87 197 198/ 133 229 230/ 194 6 7/ 2 38 39/ 6 70 71/ 14 102 103/3 0 134 135/ 54 166 167/ 88 198 199/ 135 230 231/ 197 7 8/ 2 39 40/ 6 71 72/ 15 103 104/3 0 135 136/ 55 167 168/ 89 199 200/ 137 231 232/ 199 8 9/ 2 40 41/ 6 72 73/ 15 104 105/ 31 136 137/ 55 168 169/ 91 200 201/ 139 232 233/ 201 9 10/ 2 41 42/ 6 73 74/ 15 105 106/ 32 137 1 38/ 56 169 170/ 92 201 202/ 140 233 234/ 203 10 11/ 2 42 43/ 7 74 75/ 16 106 107/ 32 138 139/ 57 170 171/ 93 202 203/ 142 234 235/ 205 11 12/ 2 43 44/ 7 75 76/ 16 107 108/ 33 139 140/ 58 171 172/ 95 203 204/ 144 235 236/ 208 12 13/ 2 44 45/ 7 76 77/ 16 108 109/ 33 140 141/ 59 1 72 173/ 96 204 205/ 146 236 237/ 210 13 14/ 2 45 46/ 7 77 78/ 17 109 110/ 34 141 142/ 60 173 174/ 97 205 206/ 147 237 238/ 212 14 15/ 3 46 47/ 7 78 79/ 17 110 111/ 35 142 143/ 61 174 175/ 99 206 207/ 149 238 239/ 215 15 16/ 3 47 48/ 8 79 80/ 18 111 112/ 35 143 144/ 62 175 176/ 100 207 208/ 151 239 240/ 217 16 17/ 3 48 49/ 8 80 81/ 18 112 113/ 36 144 145/ 63 176 177/ 101 208 209/ 153 240 241/ 219 17 18/ 3 49 50/ 8 81 82/ 19 113 114/ 37 145 146/ 64 177 178/ 103 209 210/ 155 241 242/ 221 18 19/ 3 50 51/ 8 82 83/ 19 114 115/ 38 146 147/ 65 178 179/ 104 210 211/ 156 242 243/ 224 19 20/ 3 51 52/ 9 83 84/ 20 115 116/ 38 147 148/ 66 179 180/ 106 211 212/ 158 243 244/ 226 20 21/ 3 52 53/ 9 84 85/ 20 116 117/ 39 148 149/ 67 180 181/ 107 212 213/ 160 244 245/ 229 21 22/ 3 53 54/ 9 85 86/ 21 117 118/ 40 149 150/ 68 181 182/ 109 213 214/ 162 245 246/ 231 22 23/ 3 54 55/ 9 86 87/ 21 118 119/ 40 150 151/ 69 182 183/ 110 214 215/ 164 246 247/ 233 23 24/ 4 55 56/ 10 87 88/ 22 119 120/ 41 151 152/ 71 183 184/ 111 215 216/ 166 247 248/ 236 24 25/ 4 56 57/ 10 88 89/ 22 120 121/ 42 152 153/ 72 184 185/ 113 216 21 7 / 168 248 249/ 238 25 26/ 4 57 58/ 10 89 90/ 23 121 122/ 43 153 154/ 73 185 186/ 114 217 218/ 170 249 250/ 241 26 27/ 4 58 59/ 10 90 91/ 23 122 123/ 44 154 155/ 74 186 187/ 116 218 219/ 172 250 251/ 243 27 28/ 4 59 60/ 11 91 92/ 24 123 124/ 44 155 156/ 75 187 188/ 117 219 220 / 174 251 252/ 246 28 29/ 4 60 61/ 11 92 93/ 24 124 125/ 45 156 157/ 76 188 189/ 119 220 221/ 176 252 253/ 248 29 30/ 4 61 62/ 11 93 94/ 25 125 126/ 46 157 158/ 77 189 190/ 121 221 222/ 178 253 254/ 251 30 31/ 4 62 63/ 12 94 95/ 25 126 127/ 47 158 159/ 78 190 191/ 122 222 223/ 180 254 255/ 253 31 32/ 5 63 64/ 12 95 96/ 26 127 128/ 48 159 160/ 80 191 192/ 124 223 224 / 182 255 256/256 table 10 intensity index vs. pwm pulse width (normal polarity ) index lin/log index lin/log index lin/log index lin/log index lin/ log index lin/log index lin/ log index lin/log 0 256/ 256 32 224/ 251 64 192/ 244 96 160/ 230 128 128/ 208 160 96/ 175 192 64/ 131 224 32/ 72 1 255/ 256 33 223/ 251 65 191/ 243 97 159/ 229 129 127/ 207 161 95/ 174 193 63/ 129 225 31/ 70 2 254/ 256 34 222/ 251 66 190/ 243 9 8 158/ 229 130 126/ 206 162 94/ 173 194 62/ 127 226 30/ 68 3 253/ 256 35 221/ 251 67 189/ 243 99 157/ 228 131 125/ 205 163 93/ 172 195 61/ 126 227 29/ 66 4 252/ 256 36 220/ 251 68 188/ 242 100 156/ 227 132 124/ 204 164 92/ 170 196 60/ 124 228 28/ 64 5 251/ 254 37 219/ 250 69 187/ 242 101 155/ 227 133 123/ 203 165 91/ 169 197 59/ 123 229 27/ 62 6 250/ 254 38 218/ 250 70 186/ 242 102 154/ 226 134 122/ 202 166 90/ 168 198 58/ 121 230 26/ 59 7 249/ 254 39 217/ 250 71 185/ 241 103 153/ 226 135 121/ 201 167 89/ 167 199 57/ 119 231 25/ 57 8 248/ 254 40 216/ 250 72 184/ 241 104 152/ 225 136 120/ 201 168 88/ 165 200 56/ 117 232 24/ 55 9 247/ 254 41 215/ 250 73 183/ 241 105 151/ 224 137 119/ 200 169 87/ 164 201 55/ 116 233 23/ 53 10 246/ 254 42 214/ 249 74 182/ 240 106 150/ 224 138 118/ 199 170 86/ 163 202 54/ 114 234 22/ 50 1 1 245/ 254 43 213/ 249 75 181/ 240 107 149/ 223 139 117/ 198 171 85/ 161 203 53/ 112 235 21/ 48 12 244/ 254 44 212/ 249 76 180/ 240 108 148/ 223 140 116/ 197 172 84/ 160 204 52/ 110 236 20/ 46 13 243/ 254 45 211/ 249 77 179/ 239 109 147/ 222 141 115/ 196 173 83/ 159 205 51/ 10 9 237 19/ 44 14 242/ 253 46 210/ 249 78 178/ 239 110 146/ 221 142 114/ 195 174 82/ 157 206 50/ 107 238 18/ 41 15 241/ 253 47 209/ 248 79 177/ 238 111 145/ 221 143 113/ 194 175 81/ 156 207 49/ 105 239 17/ 39 16 240/ 253 48 208/ 248 80 176/ 238 112 144/ 220 144 112/ 193 176 80 / 155 208 48/ 103 240 16/ 37 17 239/ 253 49 207/ 248 81 175/ 237 113 143/ 219 145 111/1 92 177 79/ 153 209 47/ 101 241 15/ 35 18 238/ 253 50 206/ 248 82 174/ 237 114 142/ 218 146 110/ 191 178 78/ 152 210 46/ 100 242 14/ 32 19 237/ 253 51 205/ 247 83 173/ 236 115 141/ 218 147 109/ 190 179 77/ 150 211 45/ 98 243 13/ 30 20 236/ 253 52 204/ 247 84 172/ 236 116 140/ 217 148 108/ 189 180 76/ 149 212 44/ 96 244 12/ 27 21 235/ 253 53 203/ 247 85 171/ 235 117 139/ 216 149 107/ 188 181 75/ 147 213 43/ 94 245 11/ 25 22 234/ 253 54 202/ 247 86 170/ 235 118 1 38/ 216 150 106/ 187 182 74/ 146 214 42/ 92 246 10/ 23 23 233/ 252 55 201/ 246 87 169/ 234 119 137/ 215 151 105/ 185 183 73/ 145 215 41/ 90 247 9/ 20 24 232/ 252 56 200/ 246 88 168/ 234 120 136/ 214 152 104/ 184 184 72/ 143 216 40/ 88 248 8/ 18 25 231/ 252 57 199/ 246 89 167/ 233 121 135/ 213 153 103/ 183 185 71/ 142 217 39/ 86 249 7/ 15 26 230/ 252 58 198/ 246 90 166/ 233 122 134/ 212 154 102/ 182 186 70/ 140 218 38/ 84 250 6/ 13 27 229/ 252 59 197/ 245 91 165/ 232 123 133/ 212 155 101/ 181 187 69/ 139 219 37/ 82 251 5/ 10 28 228/2 52 60 196/ 245 92 164/ 232 124 132/ 211 156 100/ 180 188 68/ 137 220 36/ 80 252 4/ 8 29 227/ 252 61 195/ 245 93 163/ 231 125 131/ 210 157 99/ 179 189 67/ 135 221 35/ 78 253 3/ 5 30 226/ 252 62 194/ 244 94 162/ 231 126 130/ 209 158 98/ 178 190 66/ 134 222 34/ 76 254 2/ 3 31 225/ 251 63 193/ 244 95 161/ 230 127 129/ 208 159 97/ 176 191 65/ 132 223 33/ 74 255 0/ 0 table 1 1 intensity index vs. pwm pulse width (inverted polarity) recommended/default settings are inverted polarity (to take advantage from high sink current capabi lity) and logarithmic mode (due to the non - linear response of the human eye).
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 31 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 3.17 smart wake up the sx8638 offers a smart wake up mechanism (up to 6 keys) which allows waking - up from the doze low power mode to the active mode in a secure/controlled way a nd not by any unintentional sensor activation. until the full correct wake - up sequence is entered, the sx8638 will remain in doze mode. any wrong key implies the whole sequence to be entered again. please note that each key touch must be followed by a rel ease to be validated. hence if a proximity sensor and a touch button part of the wake - up sequence are interleaved on the pcb (ie if you cannot touch the button without triggering proximity detection) the smart wake up feature cannot be used since the proxi mity sensor is not ?released? before the buttons are touched. in this case the smart wakeup sequence must be turned off. t he smar t wake - up mechanism can also be disabled which implies that doze mode can hence only be exited from gpi or i2c command .
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 32 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 4 p in descriptions 4.1 introduction this chapter describes briefly the pins of the sx8638 , the way the pins are protected, if the pins are analog, digital, require pull up or pull down resisto rs and show control signals if these are available. 4.2 asi pins cap0, cap 1, ..., cap7 the capacitance sensor pins (cap0, cap1, ..., cap7 ) are connected directly to the asi circuitry which converts the sensed capacitance into digital values . the capacitance sensor pins which are not used should be left open. the enabled cap pins need be connected directly to the sensors without significant resistance (typical below some ohms , connection vias are allowed ). the capacitance sensor pins are protected to vana and ground. figure 35 shows the simplified d iagram of the cap0, cap1, ..., cap7 pins. sx863 8 sensor asi cap x cap_in x vana note : x = 0, 1,2,?7 figure 35 simplified diagram of cap0, cap1, ..., cap7 cn, cp the cn and the cp pins are connected to the asi circuitry. a 1nf sampling capacitor between cp and cn needs to be placed as close as possible to the sx8638 . the cn and cp are protected to vana and ground. figure 36 shows the simplified diagram of the cn and cp pins.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 33 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity sx863 8 asi cp vana cn vana figure 36 simplified diagram of cn and cp 4.3 host interface pins t he host interface consists of the interrupt pin intb , a reset pin resetb and the standard i2c pins : scl and sda. intb the intb pin is an open drain output that requires an external pull - up resist or (1..10 kohm). the intb pin is protected to vdd using dedicated devices . the intb pin has diode protected to ground. figure 37 shows a simplified diagram of the intb pin. vdd r_int intb sx863 8 int to host figure 37 simplified diagram of intb
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 34 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity scl the scl pin is a high impedance input pin. the scl pin is protected to vdd, using dedicated devices , in order to conform to standard i2c slave specifications. the scl pin has diode protected to ground. an exter nal pull - up resistor (1..10 kohm) is required on this pin . figure 38 shows the simplified diagram of the scl pin. vdd r_ scl s cl sx863 8 from host s cl _in figure 38 simplified diagram of scl sda sda is an io pin th at can be used as an open drain output pin with ex ternal pull - up resistor or as a high impedance input pin. the sda io pin is protected to vdd, using dedicated devices , in order to conform to standard i2c slave specifications. the sda pin has diode protect ed to ground. an external pull - up resistor (1..10 kohm) is required on this pin . figure 39 shows the simplified diagram of the sda pin. vdd r_ sda sda sx863 8 sda_out from/ to host sda_in figure 39 simplified diagram of sda
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 35 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity resetb the resetb pin is a high impedance input pin. the resetb pin is protected to vdd using dedicated devices . the resetb pin has diode protected to ground. figure 40 shows the simplified diagram of the resetb pin controlled by the host. vdd r_ resetb resetb sx863 8 from host resetb _in figure 40 simplified diagram of resetb controlled by host figure 41 shows the resetb without host control. vdd resetb sx863 8 resetb _in figure 41 simplified diagram of resetb without host control
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 36 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 4.4 power management pins the power management pins consist of the power, ground and regulator pins. vdd vdd is a power pin and is the main power supply for the sx8638 . vdd has protection to ground. figure 42 shows a simplified diagram of the vdd pin. vdd sx863 8 vdd figure 42 simplified diagram of vdd gnd the sx8638 has four ground pins all named gnd. the se pins and the package center pad n eed to be connecte d to ground potential. the gnd has protection to vdd. figure 43 shows a simplified diagram of the gnd pin. vdd sx863 8 gnd gnd figure 43 simplified diagram of gnd
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 37 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity vana, vdig the sx8638 has on - chip regulators for internal use ( pins vana and vdig). vana and vdig have protection to vdd and to gnd. the output of the regulators needs to be de - coupled with a small 100nf capacitor to ground. figure 44 shows a simplified diagram of the vana and vdig pin. vdd sx863 8 gnd vdig vdd gnd vana vana vdig cvdig cvana figure 44 simplified diagram of vana and vdig 4.5 general purpose io pins the sx8638 has 8 general purpose input/output (gpio) pins. all the gpio pins have pro tection to vdd and gnd. the gpio pins can be configured as gpi, gpo or gpp. figure 45 shows a simplified diagram of the gpio pins. sx 8638 vdd rup ctrl rdown gpio7...0 ctrl gpo, gpp vdd pwm gpi gpo, gpp vdd figure 45 simplified diagram of gpio pins
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 38 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 5 d etailed c onfiguration descrip tions 5.1 introduction t he sx8638 configuration parameters are ta ken from the q s m or the nvm and loaded into the spm as explained in the chapter ?functional description?. this chapter describes the details of the configuration p arameters of the sx8638 . . the spm is split by functionality into 6 configuration sections: ? general section: operating modes, ? capacitive sensors section: related to lower level capacitive sensing, ? button : related to the conversion from sensor data toward s button information, ? slider : related to the conversion from sensor data towards slider information, ? mapping : related to mapping of button and slider information towards wake - up and gpio pins, ? gpio : related to the setup of the gpio pins. the total address space of the spm and the nvm is 128 bytes, from address 0x00 to address 0x7f. two types of memory addresses, data are accessible to the user. ? ?application data?: application dependent data that need to be configured by the user. ? ?reserved?: data that need to be maintained by the user to the qsm default values (i.e. when nvm is burned). the table 12 and table 13 resume the complete spm address space and show the ?application data? and ?reserved? addresses , the functional split and the default values (loaded from the qsm).
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 39 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity address name default qsm value address name default qsm value 0x00 reserved 0xxx 0x20 reserved 0x00 0x01 reserved 0xxx 0x21 button btncfg 0x30 0x02 reserved 0x 31 0x22 btn avg thresh 0x50 0x03 reserved 0xxx 0x23 btn comp neg thresh 0x50 0x04 general i2caddress 0x2b 0x24 btn comp negcntmax 0x01 0x05 activescanperiod 0x02 0x25 btnhysteresis 0x0a 0x06 dozescanperiod 0x0d 0x26 btnstuckattimeout 0x00 0x07 passivetimer 0x0 0 0x27 slider sldcfg 0x00 0x08 reserved 0x00 0x28 sldstuckattimeout 0x00 0x09 capacitive sensors capmodemisc 0x01 0x29 sld hysteresis 0x03 0x0a reserved 0x00 0x2a reserved 0xff 0x0b capmode7_4 0xa a 0x2b sldnormmsb 0x01 0x0c capmode3_0 0 x a5 0x2c sldnormlsb 0x80 0x0d capsensitivity0_1 0x00 0x2d sldavgthresh 0x50 0x0e capsensitivity2_3 0x00 0x2e sldcompnegthresh 0x50 0x0f capsensitivity4_5 0x00 0x2f sldcompnegcntmax 0x01 0x10 capsensitivity6_7 0x00 0x30 sldmovethresh 0x02 0x11 reserved 0x00 0x31 reserved 0x00 0x12 reserved 0x00 0x32 reserved 0x00 0x13 capthresh0 0xa0 0x33 mapping mapwakeupsize 0x00 0x14 capthresh1 0xa0 0x34 mapwakeupvalue0 0x00 0x15 capthresh2 0xa0 0x35 mapwakeupvalue1 0x00 0x16 capth resh3 0xa0 0x36 mapwakeupvalue2 0x00 0x17 capthresh4 0xa0 0x37 mapautolight0 0xcc 0x18 capthresh5 0xa0 0x38 mapautolight1 0xcc 0x19 capthresh6 0xa0 0x39 mapautolight2 0xcc 0x1a capthresh7 0xa0 0x3a mapautolight3 0x10 0x1b reserved 0xa0 0x3b mapautolightgrp0msb 0x4 0 0x1c reserved 0xa0 0x3c mapautolightgrp0lsb 0x00 0x1d reserved 0xa0 0x3d mapautolightgrp1msb 0x00 0x1e reserved 0xa0 0x3e mapautolightgrp1lsb 0x00 0x1f cappercomp 0x00 0x3f mapsegmenthysteresis 0x02 table 12 spm address map: 0x00?0x3f note ? ?0xxx?: write protected data
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 40 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity address name default qsm value address name default qsm value 0x40 gpio gpiomode7_4 0x00 0x60 gpio gpiodectime1_0 0x44 0x41 gpiomode3_0 0x00 0x61 gpiooffd elay7_6 0x00 0x42 gpiooutpwrup 0x00 0x62 gpiooffdelay5_4 0x00 0x43 gpioautolight 0xff 0x63 gpiooffdelay3_2 0x00 0x44 gpiopolarity 0x00 0x64 gpiooffdelay1_0 0x00 0x45 gpiointensity on 0 0xff 0x65 gpiopullupdown7_4 0x00 0x46 gpiointensity on 1 0xff 0x66 gpiopullupdown3_0 0x00 0x47 gpiointensityon2 0xff 0x67 gpiointerrupt7_4 0x00 0x48 gpiointensityon3 0xff 0x68 gpiointerrupt3_0 0x00 0x49 gpiointensity on 4 0xff 0x69 gpiodebounce 0x00 0x4a gpiointensity on 5 0xff 0x6a reserved 0x00 0x4b gpiointensity on 6 0xff 0x6b reserved 0x00 0x4c gpiointensity on 7 0xff 0x6c reserved 0x00 0x4d gpio intensityoff 0 0x00 0x6d reserved 0x00 0x4e gpio intensityoff 1 0x00 0x6e reserved 0x00 0x4f gpio intensityoff 2 0x00 0x6f reserved 0x50 0x5 0 gpio intensityoff 3 0x00 0x70 capproxenable 0x46 0x51 gpio intensityoff 4 0x00 0x71 reserved 0x10 0x52 gpio intensityoff 5 0x00 0x72 reserved 0x45 0x53 gpio intensityoff 6 0x00 0x73 reserved 0x02 0x54 gpio intensityoff 7 0x00 0x74 reserved 0xff 0x55 reserved 0xff 0x75 reserved 0xff 0x56 gpiofunction 0x00 0x76 reserved 0xff 0x57 gpioincfactor 0x00 0x77 reserved 0xd5 0x58 gpiodecfactor 0x00 0x78 reserved 0x55 0x59 gpioinctime7_6 0x00 0x79 reserved 0x55 0x5a gpioinctime5_4 0x0 0 0x7a reserved 0x7f 0x5b gpioinctime3_2 0x00 0x7b reserved 0x23 0x5c gpioinctime1_0 0x00 0x7c reserved 0x22 0x5d gpiodectime7_6 0x44 0x7d reserved 0x41 0x5e gpiodectime5_4 0x44 0x7e reserved 0xff 0x5f gpiodectime3_2 0x44 0x7f spmcrc * 0xa3 table 13 spm address map: 0x40?0x7f note * ? spmcrc : crc depending on spm content, updated in active or doze mode.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 41 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 5.2 general parameters general parameters address name b its description 0x04 i2c a ddress 7 reserved 6:0 defines the i2c address (default 0x2b). the i2c address will be active after a reset. 0x05 activescanperiod 7:0 active mode scan period ( figure 7 ) 0x00: r eserved 0x01: 15 ms 0x02: 30ms (default) ? 0xff: 255 x 15 ms 0x06 dozescanpe riod 7:0 doze mode scan period ( figure 7 ) 0x00: r eserved 0x01: 15 ms ? 0x0d: 195 ms (default) ? 0xff: 255 x 15 ms 0x07 passivetimer 7:0 passive timer on button and slider information ( figure 8 ) 0x00: o ff (d efault) 0x01: 1 second ? 0xff: 255 seconds table 14 general parameters
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 42 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 5.3 capacitive sensors parameters capacitive sensors parameters address name bits description 0x09 capmodemisc 7:3 reserved 2:0 individualsensitivity defi nes common sensitivity for all sensors or individual sensor sensitivity. 001: common settings (capsensitivity0_1[7:4]) 100: individual cap sensitivity settings (capsensitivityx_x) else : reserved 0x0a reserved 7:0 reserved 0x0b cap mode7_4 7:6 cap7 mode d efines the mode of the cap pin. 00: d isabled 01: button 10: slider 11: reserved default slider 5:4 cap6 mode slider 3:2 cap5 mode slider 1:0 cap4 mode slider 0x0c capmode3_0 7:6 cap3 mode slider 5:4 cap2 mode slider 3:2 cap1 mode button 1:0 cap0 mode button 0x0d capsensitivity0 _ 1 7:4 cap0 sensitivity - common s ensitivity defines the sensitivity. 0x0: m inimum (default) 0x7: m aximum 0x8?0xf: r eserved 3:0 cap1 s ensitivity 0x0e capsensitivity2 _ 3 7:4 cap2 s ensitivity 3:0 cap3 s ensitivity 0x0f capsensitivity4 _ 5 7:4 cap4 s ensitivity 3:0 cap5 s ensitivity 0x10 capsensitivity6 _ 7 7:4 cap6 s ensitivity 3:0 cap7 s ensitivity 0x11 reserved 7:0 reserved 0x12 reserved 7:0 reserved 0x13 cap thresh 0 7:0 cap0 touch t hre shold defines the touch threshold ticks. 0 x00: 0, 0x01: 4, ? 0xa0: 640 (default), ? 0xff: 1020 0x14 cap thresh 1 7:0 cap1 touch t hreshold 0x15 capthres h 2 7:0 cap2 touch t hreshold 0x16 capthres h 3 7:0 cap3 touch t hreshold 0x17 capthres h 4 7:0 cap4 t ouch t hreshold 0x18 capthres h 5 7:0 cap5 touch t hreshold 0x19 capthres h 6 7:0 cap6 touch t hreshold 0x1a capthres h 7 7:0 cap7 touch t hreshold 0x1b reserved 7:0 reserved 0x1c reserved 7:0 reserved 0x1d reserved 7:0 reserved 0x1e reserved 7:0 rese rved
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 43 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity capacitive sensors parameters address name bits description 0x1f cappercomp 7:4 reserved 3:0 periodic offset compensation defines the periodic offset compensation . 0x0: off (default) 0x1: 1 second 0x2: 2 seconds ? 0x7: 7 seconds 0x8: 16 seconds 0x9: 18 seconds ? 0xe: 28 seconds 0xf: 60 seconds 0x70 capp roxenable 7:0 enables proximity sensing: 0x46: off 0x74: on table 15 capacitive sensors parameters capmodemisc by default t he asi is using a common sensitivity for all capacitive sensors as in the usual case overlay material and sensors sizes are about equal. the register bits capsensitivity0 _ 1 [7:4] determine the sensitivity for all sensors in common sensitivity mode. it might be required to have a different, individual, sensitivity for each cap pin (for example proximity sensor set to max sensitivity while touch sensors are set to a lower one). this can be obtained by setting capmodemisc[2:0] to ?100? the individual sensitivity mode results in longer sensing periods than required in common sensitivity mode. cap mode 7 _ 4 , cap mode 3 _ 0 : the cap pi ns can be set as a button, part of a slider or disable d depending on the application. minimum default maximum buttons zero two four slider one (of four sensors) one (of six sensors) one (of eight sensors) table 16 possible cap pin modes
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 44 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity buttons and disabled cap pins can be attributed freely (examples in figure 46 ). all buttons can be used for touch or proximity sensing, in the latter case register capproxenable needs to b e set accordingly. sx8638 cap1 (button1) cap4 (disabled) cap2 (button2) cap3 (button3) cap5 (disabled) cap6 (disabled) sx8638 cap1 (button1) cap6 (button6) cap3 (button3) cap2 (disabled) cap4 (disabled) cap5 (disabled) figure 46 button examples disabled cap pins inside the slider sensor attribution sequence are allowed, but cap buttons inside a slider are not allowed (see example figure 47 with cap 3 in a correct and a not allowed configuration ). sx 8638 cap 1 ( button1) cap2 (sld0) cap3 (disabled) cap4 (sld1) cap5 (sld2) cap6 (sld3) sx 8638 cap 2 ( sld 0 ) cap3 (button3) cap4 (sld1) cap5 (sld2) cap6 (sld3) min max figure 47 button and slider good/bad configuration examples (i) the physical order of the slider sensors on the pcb should correspond to the incremental cap pin numbers. crossing slider pcb sensors and cap number is not allowed . figure 48 shows a valid configuration and a wrong configuration where cap 5 and cap 6 are not routed correctly on the pcb.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 45 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity sx 8638 cap 2 ( sld0) cap3 (disabled ) cap4 (sld 1) cap5 (sld 2) cap6 (sld 3) sx8638 cap2 (sld0) cap3 (disabled) cap4 (sld 1) cap5 (sld2) cap6 ( sld3) min max figure 48 button and slider good/bad configuration examples (ii) the minimum position of the slider is associated to the cap pin, attributed to the slider , with the lowest index (in figure 48 this is cap2). the maximum position of the slider is associated to the cap pin, attributed to the slider , with the highest index (in figure 48 this is cap6). capsensitivity0 _ 1 , capsensitivity2 _ 3 , capsensitivity4 _ 5 , capsensitivity6 _ 7 , capproxenable : the sensitivity of the sensors can be set between 8 values. the higher the sensitivity is set the larger the value of the ticks will be. the minimum sensitivity can be used for thin overlay materials and large sensors , while the maximum sensitivity is required for thicker overlay and smaller sensors or proximity sensing. the required sensitivity needs to be determined during a product development phase. too low sensitivity settings result in missing touches. too high s ensitivity settings will result in fault detection of fingers hovering above the touch sensors. the sensitivity is identical for all sensors in common sensitivity mode using the bits capsensitivity0_1[7:4] and can be set individually using register capmode misc [2:0]. the maximum number of ticks that can be obtained depends on the selected sensitivity and if proximity sensing is enabled. this is illustrated in table 17 . sensitivity approximate maximum tick level (capproxenable = o ff ) approximate maximum tick level (capproxenable = on) 0 1000 4 000 1 2000 8 000 2 3000 12 000 3 4000 16 000 4 5000 20 000 5 6000 24 000 6 7000 28 000 7 8000 32 000 table 17 asi maximum tick levels
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 46 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity cap thresh 0 , cap thresh 1 , cap thresh 2 , cap thresh 3 , cap thresh 4 , cap thresh 5 , cap thresh 6 , cap thresh 7 : for each cap pin a threshold level can be set individually. the threshold levels are used by the sx8638 for making touch and release decisions on e.g. touch or no - touch. the details are explained in the sections for buttons and slider . cappercomp : the sx8638 offers a periodic offset compensation for applications which are subject to substantial environmental changes. the period ic offset compensation is done at a defined interval and only if slider and buttons are released.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 47 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 5.4 button parameters button parameters address name bits description 0x21 btncfg 7:6 defines the buttons events reporting method. 00: m ultiple report ing of all touches and releases (default) 01: s ingle report in g of the first button touch. n ext button touches and releases are ignored until release of the first button . 10: reserved 11: reserved 5:4 defines the b uttons interrupt (for all buttons) 00 : interrupts masked 01 : triggered on touch 10 : triggered o n release 11 : triggered on touch and release (default) 3 :2 defines the number of samples at the sca n period for determining a release 00: off , use incoming sample (default) 01: 2 samples debounce 1 0 : 3 samples debounce 1 1 : 4 samples debounce 1 :0 def ines the number of samples at the scan period for determining a touch 00: off , use incoming sample (default) 01: 2 samples debounce 1 0 : 3 samples debounce 1 1 : 4 samples debounce 0x22 btn avgthresh 7:0 defines the positive threshold for disabling the proces sing filter averaging. if ticks are above the threshold, then the averaging is suspended 0 x00: 0 0x01: 4 ? 0x50: 320 (default) ? 0xff: 1020 0x23 btn comp neg thresh 7:0 defines the negative offset compensation threshold. 0 x00: 0 0x01: 4 ? 0x50: 320 (default) ? 0xff: 1020 0x24 btn comp negcntmax 7:0 defines the number of ticks (below the negative offset compensation threshold) which will initiate an offset compensation. 0x00: reserved 0x01: 1 sample (default) ? 0xff - > samples 0x25 btnhysteresis 7:0 defines the button hysteresis corresponding to a percentage of the cap thresholds (defined in table 18). 0x00: 0% ? 0x0a: 10% (default) ? 0x64: 100% a ll buttons use the same hysteresis 0x26 btnstuckattimeout 7:0 defines the stuck at timeou t . 0x0 0 : off (default)
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 48 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity button parameters address name bits description 0x01: 1 second ? 0xff: 255 seconds table 18 button configuration parameters please note that proximity sensors are configured as buttons and operate exactly the same way as touch buttons. all the parameters and procedures described below apply similarly. a reliable button operation requires a coherent setting of the registers. figure 49 shows a n example of a touch and a release. the ticks will vary slightly around the zero idle s tate. when the touch occurs the ticks will rise sharply. at the release of the button the ticks will go down rapidly and converge to the idle zero value. time 0 ticks_diff btnhysteresis btnhysteresis = no-touch touch (touch debounce = 1) = touch (release debounce = 0) release capthreshold = scan events @ scan period figure 49 t ouch and release e xample as soon a s the ticks become larger than the cap threshold s (see registers of the previous section) plus the hysteresis (defi ne d in register btnhysteresis ) the debounce counter starts. in the example of figure 49 the touch i s validated after 2 samples ( btncfg [ 1 :0] = 0 1). the release is detected immediately ( btncfg [3 :2 ] = 0 0) at the first sample which is below the threshold minus the hysteresis. btncfg the sx8638 can report all touches of multiple fingers or the sx8638 ca n be set to report only the first detected touch. in the later case all succeeding touches are ignored. the very first touch should be released before a next touch will be detected. the user can select to have the interrupt signal on touching a button, re leasing a button or both in noisy environments it may be required to debounce the touch and release detection decision. in case the debounce is enabled the sx8638 will count up to the number of debounce samples btncfg [ 1 :0] , btncfg [ 3:2 ] before taking a t ouch or release decision. the sample period is identical to the scan period. btn avgthresh small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 49 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity in case the ticks get slightly positive this is considered as normal operation. very large positive tick values indicate a valid touch. the averaging filter is disabled as soon as the average reaches the value defined by btn avgthresh . this mechanism avoids that a valid touch will be averaged and finally the tick diff erence becomes zero. in case three or more sensors reach the btn avgthresh value simultaneously then the sx8638 will start an offset compensation procedure. small environmental and system noise cause the ticks to vary slowly around the zero idle mode valu e. in case the ticks get slightly negative this is considered as normal operation. however large negative values will trigger an offset compensation phase and a new set of dcvs will be obtained. the decision to trigger a compensation phase based on negativ e ticks is determined by the value in the register btn comp neg thresh and by the number of ticks below the negative thresholds defined in register btn compnegcntmax. an example is shown in figure 50. time 0 ticks_diff compnegcnt = 1, 2,... compnegthreshold = ticks < compnegthreshold = ticks, no-touch offset compensation compnegcnt > compnegcntmax figure 50 negative ticks offset compensation trigger btn comp neg thresh small negative ticks are considered as normal operation and will occur very often. larger negative ticks however need to be avoided and a conveni ent method is to trigger an offset compensation phase. the new set of dcv will assure the idle ticks will be close to zero again. a trade - off has to be found for the value of this register. a negative threshold too close to zero will trigger a compensation phase very often. a very negative threshold will never trigger. btn comp negcntmax as soon as the ticks get smaller than the negative threshold the negative counter starts to count. if the counter goes beyond the negative counter max then the offset compe nsation phase is triggered. the recommended value for this register is ?1? which means that the offset compensation starts on the first tick below the negative threshold. btnhysteresis the hysteresis percentage is identical for all buttons. a touch is d etected if the ticks are getting larger as the value defined by: capthreshold + cap threshold * hysteresis. a release is detected if the ticks are getting smaller as the value defi ne d by: capthreshold - cap threshold * hysteresis. btnstuckattimeout the s tuckat timer can avoid sticky buttons .
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 50 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity if the stuckat timer is set to one second then the touch of a finger will last only for one second and then a compensation will be performed and button hence considered released, even if the finger remains on the butt on for a longer time. after the actual finger release the button can be touched again and will be reported as usual. in case the stuckat timer is not required it can be set to zero.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 51 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 5.5 slider parameters slider parameters address name bits description 0x2 7 sldcfg 7:4 reserved 3 :2 defines the number of samples at the sca n period for determining a release 00: off , use incoming sample (default) 01: 2 samples debounce 1 0 : 3 samples debounce 1 1 : 4 samples debounce 1 :0 defines the number of samples at the scan period for determining a touch 00: off , use incoming sample (default) 01: 2 samples debounce 1 0 : 3 samples debounce 1 1 : 4 samples debounce 0x28 sld stuckattimeout 7:0 defines the stuck at timeout . 0x0 0 : off (default) 0x01: 1 second ? 0xff: 255 seconds 0x29 sld hysteresis 7:0 defines the slider touch/release hysteresis . 0 x00: 0 0x01: 4 ? 0x03: 12 (default) ? 0xff: 1020 0x2b sld norm msb 7:0 slider norm msb defines the 16 bits slider norm (default 0x0180) 0x2c sld norm lsb 7:0 slider norm lsb 0x2d sldav gthresh 7:0 defines the positive threshold for disabling the processing filter averaging. if ticks are above the threshold, then the averaging is suspended 0 x00: 0 0x01: 4 ? 0x50: 320 (default) ? 0xff: 1020 0x2e sldcomp neg thresh 7:0 defines the negative o ffset compensation threshold. 0 x00: 0 0x01: 4 ? 0x50: 320 (default) ? 0xff: 1020 0x2f sldcomp negcntmax 7:0 defines the number of ticks (below the negative offset compensation threshold) which will initiate an offset compensation. 0x00: reserved 0x01: 1 sa mple (default) ? 0xff: 255 samples 0x30 sldmovethresh 7:0 defines the threshold for detecting a move high or move low. the threshold is a percentage of the maximum slider position. 0x00: 0% ? 0x02: 2% (default)
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 52 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity slider parameters address name bits description ? 0x64: 100% a succeeding position differen ce, at the scan period, above the threshold is considered as a move high or move low. table 19 slider parameters
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 53 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity the pressure represents the finger touch on the sensors of the slider and it used to determine if a slider is touche d or released. ? = ? = 1 0 )) ( ) ( _ ( n i i capthresh i diff ticks e sldpressur - n is the number of sensors, - a senso r with ticks smaller than the capt hreshold is not taken into accou nt for calculating the p ressure in case the pressure equals zero the slider status is released. in case the p ressure is larger as the slider hysteresis the slider status is touched. t he position of a finger on a slider is calculated by the centre of gravity algorithm . ? = ? = ? ? ? = 1 0 1 0 )) ( ) ( _ ( )) ( ) ( _ ( * 32 n i n i i capthresh i diff ticks i capthresh i diff ticks i sldnorm sldpos - n is the number of sensors, - a senso r with ticks smaller than th e capt hreshold is not taken into accou nt for calculating the position, - sldnorm [15:0] i s a 16 bit number determined by sld normm sb [15:8] and sld norml sb [7:0]. - sldpos is the slider position (16 bits) which can be read by the host over the i2c registers sl d posmsb and sldposl sb .... x ... position cap0 cap1 cap5 cap 4 cap 3 cap 2 figure 51 slider position figure 51 shows an example of a slider composed of 6 sensors (cap0, cap1? cap5). the default slider norm value 12 (sldnormm sb = 0x01, sldnorml sb = 0x80) , is taken for the example. a touch on c ap0 gives the slider position: 0 . a touc h on cap1 gives the slider position: 12 . a touc h on cap5 gives the slider position: 60 . if a touch occurs on cap0 and cap1 the centre of gravity alg orithm will interpolate. assuming the touch is identically distributed on cap0 and c ap1 then the position will be: 6 assuming the touch is identically distributed on cap1 and cap2 then the position wi ll be: 18 assuming the touch is identically distributed on cap 4 and cap 5 then the position will be: 5 4 the maximum slider position (for this example) that can be obtained is 60. the minimum position of a slider e quals 0.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 54 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity the maximum position ( sldposmax ) is defined by: ( ) 1 32 ? = n sldnorm sldposmax with: n i s the number of sensors in the slider slow varying slider ticks due to environmental changes are handled as buttons in the previous section. if the ticks pass below the slider negative threshold for more than the compensation negative max counter then a n offset compensation phase will be triggered. if the ticks pass above the slider average positive threshold then the averaging filters will be held. a finger that moves very slowly over the slider is not considered as a movement . the status move low and m ove high will not be set. a finger that moves faster on the slider will change the movement status. a movement is detected if the difference of the position for two succeeding samples at the scanni ng rate goes beyond the movement threshold ( sldmove thresh ). a large movement threshold requires very rapid finger m ovements, while a small mov e ment thresho ld detects more easily movements but gets sensitive to noise variations as well.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 55 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 5.6 mapping parameters mapping parameters address name bits description 0x 33 map wakeupsize 7:3 reserved 2:0 doze - > active wake up sequence size . 0: a ny sensor event (default) 1: k ey0 2: k ey0 , key1 ? 6: ke y0, key1,?key5 7: no sensor event, only gpi or i2c cmd can exit doze mode each key must be followed by a release to be validated. any other sensor event before the release is ignored. any wrong key implies the whole sequence to be entered again. 0x34 map wakeupvalue0 7:4 key5 defines the sensor event associated to each key. 0x00: btn0 (default) 0x01: btn1 ? 0x07: btn7 0x0 8?0xa : reserved 0x 0c: s lider t ouch 0x 0 d : move low 0x0e: m ove high 0x 0 f: reserved 3:0 key 4 0x35 map wakeupvalue1 7:4 key 3 3:0 key 2 0x36 map wakeupvalue2 7:4 key 1 3:0 key 0 0x37 mapautolight0 7:4 gpio[7] d efines the mapping between gpos (with autolight on) and sensor events. 0x00: btn0 (default) 0x01: btn1 ? 0x07: btn7 0x08?0x0b : reserved 0x0c: g roup0 as defined by mapautolightgrp0 0x 0 d : g roup1 as defined by mapautolightgrp1 0x0e: move low 0x0f: m o ve high several gpos can be mapped to the sam e sensor event and will be controlled simultaneously. 3:0 gpio[6] 0x38 mapautolight1 7:4 gpio[5] 3:0 gpio[4] 0x39 mapautolight2 7:4 gpio[3] 3:0 gpio[2] 0x3a mapautolight3 7:4 gpio[1] 3:0 gpio[0] 0x3b mapautolightgrp0msb 7 reserved 6 segment defines group0 sensor events: 0: off (default) 1: on if any of the enabled sensor events occurs the group0 event will occur as well. all sensors events within the group can be independently set except slider event segment which is exclusive (i e must be the only one enabled to be used) 5 move high 4 move low 3 :0 reserved 0x3c mapautolightgrp0lsb 7 btn7 6 btn6 5 btn5 4 btn4 3 btn3 2 btn2 1 btn1
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 56 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity mapping parameters address name bits description 0 btn0 0x3d mapautolightgrp1msb 7 reserved 6 slider touch defines group1 sensor events: 0: off (default) 1: on if any of the enabled sensor events occurs the group0 event will occur as well. all sensors events within the group can be independently set. 5 move high 4 move low 3 :0 reserved 0x3e map autolightgrp1lsb 7 btn7 6 btn6 5 btn5 4 btn4 3 btn3 2 btn2 1 btn1 0 btn0 0x3f mapsegmenthysteresis 7:0 defines the position hysteresis for detecting a segment change. the hysteresis is defined as a percentage of the maximum sl ider position. 0x00: 0% ? 0x02: 2% (default) ? 0x64: 100% this hysteresis applies to all segments of the slider. table 20 mapping parameters map wakeupsize the number of keys defining the wakeup sequence can be set from 1 to 6 . if the size is set to 0 then wakeup is done on any sensor event. if the size is set to 6 then wakeup is don e only by gpi or an i2c command (may be required if proximity sensing is enable, see 3.17 for more details). map w akeupvalue0 , map wakeupvalue1 , map wakeupvalue2 for the wakeup sequence btn 2 - > btn 5 - > btn 6 - > btn 0 t he required register settings are : - map wakeupsize set to 0x04, - k ey0 = 0x2 - key1 = 0x5 => mapwakeupvalue2 set to 0x52 - key2 = 0x6 - key3 = 0x0 => mapwakeupvalue2 set to 0x06
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 57 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity mapautolight0 , mapautolight1 , mapautolight2 , mapautolight3 mapautolightgrp0msb , mapautolightgrp0lsb , mapautoligh tgrp1msb , mapautolightgrp1lsb these registers define the mapping between the gpo pins (with autolight on) an d the sensor information which will control its on/off state . the mapping can be done to a specific sensor event but also on groups (in this case any sensor event in the group will control the gpo). table 21 defines for each sel ectable sensor event, which action will trigger corresponding gpo to switch on or off . mapautolight gpo on gpo off btnx touch release slider touch touch release slider move high move high move low or release slider move low move low move high or releas e slider segment segment touched segment released table 21 autolight mapping, sensor information examples: - if gp o [0] should change state accordingly to btn 4 then mapautolight3 [3:0] should be set to 0x04. - if gpo[0] should cha nge state accordingly to btn0 or btn1 then group0 can be used as following : - mapautolight3 [3:0] should be set to 0x0c (ie group0). - m apautolightgrp0 should be set to 0x 00 03 (ie btn0 or btn1) when the slider segment event is mapped, t he number of gpos m apped to it determines the number of slider segments. the gpo with the lowest pin index is mapped on the segment with the smallest positions. e.g. if two gpos (e.g. gpo[0] and g po [1]) are mapped to the slider segment event then the slider is split in two s egments . g po [0] will turn on for a touch on the slider segment [0, sldposmax /2] and gpo[1] for a touch on the slider segment [sldposmax/2, sldposmax].
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 5 8 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 5.7 gpio parameters gpio parameters address name bits description 0x40 gpiomode 7_4 7:6 gpio[7] mode defin es the gpio mode. 00: gpo (default) 01: gp p 10: gp i 11: reserved 5:4 gpio [6 ] mode 3:2 gpio [5 ] mode 1:0 gpio [4 ] mode 0x41 gpiomode 3_0 7:6 gpio [3 ] mode 5:4 gpio [2 ] mode 3:2 gpio [1 ] mode 1:0 gpio [0 ] mode 0x4 2 gpioout p wrup 7:0 gp i o[ 7] output v alue at power up d efines the values of gpo and gpp pins after power up ie default values of i2c parameters gpoctrl and gpp intensity respectively. 0: off (gpo ) / intensityoff (gpp ) (default) 1: on (gpo ) / intensity on (gpp ) bits corresponding to gpo pins with autolight on should be left to 0 . before being actually initialized gpios are set as input s with pull up. gp i o[6] output v alue at power up gp i o[5] output v alue at power up gp i o[4] output v alue at power up gp i o[3] output v a lue at power up gp i o[2] output v alue at power up gp i o[1] output v alue at power up gp i o[0] output v alue at power up 0x43 gpioautolight 7:0 gpio[7] autolight enables auto l ight in gpo mode 0 : off 1 : on (default) gpio[6 ] autolight gpio[5 ] autolight gpio[4 ] autolight gpio[3 ] autolight gpio[2 ] autolight gpio[1 ] autolight gpio[0 ] autolight 0x44 gpiopolarity 7:0 gpio[7] output p olarity defines the polarity of the gpo and gpp pins. 0: i nverted (default) 1: nor mal gpio[6] output p olarity gpio[5] output p olarity gpio[4] output p olarity gpio[3 ] output p olarity gpio[2 ] output p olarity gpio[1 ] output p olarity gpio[0 ] output p olarity 0x45 gpiointensity on 0 7:0 on intensity i ndex defines the on intensity index 0 x00: 0 0x01: 1 0x46 gpiointensity on 1 0x47 gpiointensity on 2
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 59 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity gpio parameters address name bits description 0x48 gpiointensity on 3 ? 0xff : 255 (default) 0x49 gpiointensity on 4 0x4a gpiointensity on 5 0x4b gpiointensity on 6 0x4c gpiointensity on 7 0x4d gpio intensityoff 0 7:0 off intensity i ndex defines the off intensity index 0 x00: 0 (default) 0x01: 1 ? 0xff : 255 0x4e gpio intensityoff 1 0x4f gpio intensityoff 2 0x50 gpio intensityoff 3 0x51 gpio intensityoff 4 0x52 gpio intensityoff 5 0x53 gpio intensityoff 6 0x54 gpio intensityoff 7 0x56 gpio function 7:0 gpio[7] function defines the intensity index vs pwm pulse width f unction . 0: l ogarithmic (default) 1: l inear gpio[6] function gpio[5] function gpio[4] function gpio[3] function gpio[2] function gpio[1] function gpio[0] function 0x57 gpio incfactor 7:0 gpio[7] fading increment factor d efine s the fading increment factor . 0: 1 , intensity index incremented every increment time (default) 1: 1 6 , intensity index incremented every 16 increment times gpio[6] fading increment factor gpio[5] fading increment factor gpio[4] fading increment factor gpio[3] fading increment factor gpio[2] fading increment factor gpi o[1] fading increment factor gpio[0] fading increment factor 0x58 gpio decfactor 7:0 gpio[7] fading decrement factor d efine s the fading decrement factor . 0: 1, intensity index decremented every decrement time (default) 1: 16 , intensity index dec remented every 16 decrement times gpio[6] fading decrement factor gpio[5] fading decrement factor gpio[4] fading decrement factor gpio[3] fading decrement factor gpio[2] fading decrement factor gpio[1] fading decrement factor gpio[0] fading decrement factor 0x59 gpio inctime 7_6 7:4 gpio[7] fading increment t ime defines the fading increment time .
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 60 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity gpio parameters address name bits description 3:0 gpio[6 ] fading increment t ime 0x0: off (default) 0x1: 0.5m s 0x2: 1ms ? 0xf: 7.5ms the total fading in time will be: gpioinctime*gpioincfactor* (gpiointensity on ? gpio intensityoff ) 0x5a gpio inctime 5_4 7:4 gpio[5 ] fading increment t ime 3:0 gpio[4 ] fading increment t ime 0x 5b gpio inctime 3_2 7:4 gpio[3 ] fading increment t ime 3:0 gpio[2 ] fading increment t ime 0x5c gpio inctime 1_0 7:4 gpio[1 ] fading increment t ime 3:0 gpio[0 ] fading increment t ime 0x5d gpio dectime 7_6 7:4 gpio[7] fading decrement t ime defines the fading decrement time . 0x0: off 0x1: 0.5m s 0x2: 1ms ? 0x4: 2.0ms (default) ? 0xf: 7.5ms the total fading out time will be: gpiodectime*gpiodecfactor* (gpiointensity on ? gpio intensityoff ) 3:0 gpio [6 ] fading decrement t ime 0x5e gpio dectime 5_4 7:4 gpio[5 ] fading decrement t ime 3:0 gpio[4 ] fading decrement t ime 0x5f gpio dectime 3_2 7:4 gpio[3 ] fading decrement t ime 3:0 gpio[2 ] fading decrement t ime 0x60 gpio dectime 1_0 7:4 gpio[1 ] fa ding decrement t ime 3:0 gpio[0 ] fading decrement t ime 0x61 gpio offdelay7_6 7:4 gpio[7] o ff delay defi nes the delay after gpo off trigger before fading out starts . 0x0: off (default) 0x1: 200 ms 0x2: 400 ms ? 0xf: 3000ms 3:0 gpio[6 ] off delay 0 x62 gpio offdelay5_4 7:4 gpio[5 ] off delay 3:0 gpio[4 ] off delay 0x63 gpio offdelay3_2 7:4 gpio[3 ] off delay 3:0 gpio[2 ] off delay 0x64 gpio offdelay1_0 7:4 gpio[1 ] off delay 3:0 gpio[0 ] off delay 0x65 gpiopullupdown7_4 7:6 gpio[7] pul lup/down enables pullup/dow n resistors for gpi pins . 00 : none (default) 01 : pullup 10 : pulldown 11 : reserved 5:4 gpio[6 ] pullup/down 3:2 gpio[5 ] pullup/down 1:0 gpio[4 ] pullup/down 0x66 gpiopullupdown3_0 7:6 gpio[3 ] pullup/down 5: 4 gpio[2 ] pullup/down 3:2 gpio[1 ] pullup/down 1:0 gpio[0 ] pullup/down 0x67 gpio interrupt 7_4 7:6 gpi[7] interrupt defines the gpi edge which will trigger intb falling edge and exit sleep/doze modes if relevant. 00 : none (default) 01 : rising 1 0 : falling 11 : both 5:4 gpi[6 ] interrupt 3:2 gpi[5 ] interrupt 1:0 gpi[4 ] interrupt 0x68 gpio interrupt 3_0 7:6 gpi[3 ] interrupt 5:4 gpi[2 ] interrupt 3:2 gpi[1 ] interrupt
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 61 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity gpio parameters address name bits description 1:0 gpi[0 ] interrupt 0x69 gpio debounce 7:0 gpi[7 ] debounce enables the gpi debounce (done on 10 consecutive samples at 1 ms). 0 : off (default) 1 : on gpi[6 ] debounce gpi[5 ] debounce gpi[4 ] debounce gpi[3 ] debounce gpi[2 ] debounce gpi[1 ] debounce gpi[0 ] debounce table 22 gpio parameters table 23 r esume s the applicable spm and i2c parameters for each gpio mode. gpi gpp gpo spm gpiomode x x x gpiooutpwrup x 1 x 2 gpio autoligth x gpio polarity x x gpiointensityo n x 1 x gpiointensityoff x 1 x gpiofunction x x gpioincfactor x gpiodecfactor x gpioinctime x gpiodectime x gpiooffdelay x gpiopullupdown x gpiointerrupt x gpio debounce x i2c irqsrc[4] x gpistat x gpoctrl x 3 gpppinid x gppintensity x 1 1 at power up, gpp intensity of each gpp pin is initialized with gpio intensityon or gpio intensityoff depending on gpiooutpwrup corresponding bits value . 2 only if autolight is off , else must be left to 0 (default value) 3 only if autolight is off, else ignored table 23 applicable spm/i2c parameters vs. gpio mode
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 62 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6 i2c i nterface the i2c implemented on the sx8638 is compliant with: - standard (100kb/s), fast mode (400kb/s) - slave mode - 7 bit addre ss ( default 0 x2b ). th e default address can be changed in the nvm at address 0x04. the host can use the i2c to read and write data at any time. the effective changes will be applied at the next processing phase (section 3.3 ). three types of registers are considered: - status (read). these registers give information about the s tatus of the capacitive buttons , slider , gpi s, operation modes etc? - control (read/write) . th ese registers control the soft reset, operating modes, gp ios and offset compensation. - spm gateway (read/write) . th ese registers are used for the communication between host and the spm . the spm gateway communication is done typically at power up and is not supposed to be changed when the applicati on is runnin g. the spm needs to be re - stored each time the sx8638 is powered down. the spm can be st ored permanently in the nvm memory of the sx8638 . the spm gateway communication over the i2c at power up is then not required . the i2c will be able to read and write f rom a start address and then perform read or writes sequentially, and the address increments automatically. the supported i2c access formats are described in the next sections. 6.1 i2c write the format of the i2c write is given in f igure 52 . after the start condition [s], the slave address (sa) is sent, followed by an eighth bit (?0?) indicating a write. the sx8638 then acknowledges [a] that it is being addressed, and the master sends an 8 bit data byte consisting of the sx8638 reg ister address (ra). the slave acknowledges [a] and the master sends the appropriate 8 bit data byte (wd0). again the slave acknowledges [a]. in case the master needs to write more data, a succeeding 8 bit data byte will follow (wd1), acknowledged by the sl ave [a]. this sequence will be repeated until the master terminates the transfer with the stop condition [p]. s sa 0 ra a a wd0 a wd1 a wdn a p optional optional s: start condition sa: slave address a: acknowledge ra: register address wdn: write data byte (0...n) p: stop condition from master to slave from slave to master figure 52 i2c write the register address is incremented automatically when successive regi ster data (wd1... wdn) is supplied by the master.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 63 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.2 i2c read the format of the i2c read is given in figure 53. after the start condition [s], the slave address (sa) is sent, followed by an eighth bit (?0?) indicating a write. the s x8638 then acknowledges [a] that it is being addressed, and the master responds with an 8 bit data consisting of the register address (ra). the slave acknowledges [a] and the master sends the repeated start condition [sr]. once again, the slave address (sa ) is sent, followed by an eighth bit (?1?) indicating a read. the sx8638 responds with an acknowledge [a] and the read data byte (rd0). if the master needs to read more data it will acknowledge [a] and the sx8638 will send the next read byte (rd1). this se quence can be repeated until the master terminates with a n ack [n] followed by a stop [p]. s sa 0 ra a a sr n s: start condition sa: slave address sr: repeated start condition a: acknowledge n: not acknowledge (terminating read stream) ra: register address rdn: read data byte (0...n) p: stop condition from master to slave from slave to master rd0 a optional sa 1 a rd1 optional rdn a p figure 53 i2c read
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 64 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.3 i2c r egister s overview a ddress name r/w description 0x00 irqsrc read interrupt s ource 0x01 cap statmsb read slider/button status msb 0x02 cap statlsb read button status lsb 0x03 sld posmsb read slider position msb 0x04 sld poslsb read slider position lsb 0x0 5 reserved 0x0 6 reserved 0x0 7 gpi stat read gpi status 0x0 8 spm stat read spm s tatu s 0x0 9 compopmode read/ write compensation and operating m ode 0x0 a g po ctrl read/ write gpo control 0x0b gpp pin id read/ write gpp p in s election 0x0c g pp intensity read/ write gpp intensity 0x0d spmcfg read/ write spm configuration 0x0e spmbaseaddr read/ writ e spm base address 0x0f reserved 0xac spmkeymsb read/ write spm key msb 0xad spmkeylsb read/ write spm key lsb 0xb1 softreset read/ write software reset table 24 i2c registe rs o verview
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 65 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.4 status registers address name b its d escri ption 0x00 irqsrc 7 reserved interrupt source flags 0: inactive (default) 1: active intb goes low if any of these bits is set. more than one bit can be set. reading irqsrc clears it together with intb. 6 nvm burn interrupt flag 5 spm write inter rupt flag 4 gpi interrupt flag 3 slider interrupt flag 2 b utton s i nterrupt flag 1 compensation i nterrupt flag 0 operating mode i nterrupt flag table 25 interrupt source the delay between the actual event and the flags indicating the interrupt source may be one scan period. irqsrc [ 6 ] is set once nvm burn procedure is completed . irqsrc [5] is set once spm write is effective . irqsrc [4] is set if a gpi edge as programmed in gpiointerrupt occu r red . gpistat shows the detailed status of the gpi pins. irqsrc [3] is set if a s lider event occurred (touch, release, move high, move low or position change) . capstatmsb , sldposmsb and sldposlsb show the detailed status of the s lider. irqsrc [2] is set if a button event occurr ed (touch or release if enabled) . capstatmsb and capstatlsb show the detailed status of the b uttons. irqsrc [1] is set once compensation procedure is completed either through automatic trigger or via host request . irqsrc [0] is set when actually entering a ctive or doze mode either through automa tic wakeup or via host request . compopmode shows the current operation mode.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 66 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity address name b its d escription 0x01 cap statmsb 7 reserved 6 slider move high slider move status 0: no move (default) 1: move the sta tus remains high as long as the slider is touched and no opposite move has occurred. 5 slider move low 4 slider touched slider touch status 0: released (default) 1: touched 3 :0 reserved 0x02 cap statlsb 7 button 7 touched button touch status 0: released (default) 1: t ouched 6 button 6 touched 5 button 5 touched 4 button 4 touched 3 button 3 touched 2 button 2 touched 1 button 1 touched 0 button 0 touched table 26 slider , button status msb/ls b address name b its d escription 0x0 3 sld posmsb 7:0 s lider p osition[15:8 ] shows the current (touched) or last (released) s lider position [15:0] unsigned (default 0x00) 0x0 4 sld poslsb 7:0 s lider p osition[7:0] table 27 slider positi on msb/lsb address name b its d escription 0x07 gpi stat 7 :0 gpi[ 7 :0] status status of each individual gpi pin 0: low 1: high b its of non - gpi pins are set to 0 . table 28 i2c gpi status address name b its d escription 0x08 spmstat 7 :4 reserved
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 67 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity address name b its d escription 3 nvmvalid indicates if the current nvm is valid. 0: no ? qsm is used 1: yes ? nvm is used 2:0 nvmcount indicates the number of times nvm has been burned: 0: none ? qsm is used (default) 1: once ? nvm is used if nvmvalid = 1, else qsm. 2: twice ? nvm is used if nvmvalid = 1, else qsm. 3: three times ? nvm is used if nvmvalid = 1, else qsm. 4: more than three times ? qsm is used table 29 i2c spm status
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 68 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.5 control registers address name b its d escription 0x09 compo pmode 7:3 reserved * , write only ?00000? 2 compensation indicates/triggers compensation procedure 0 : compensation completed (default) 1: read - > compensation running ; write - > trigger compensation 1:0 operating mode indicates/programs * * operati ng mode 00: active mode (default) 01: doze mode 10: sleep mode 11: reserved table 30 i2c compensation, operation modes * the reading of these reserved bits will return varying values . * * after the operating mode change (ac ti ve/doz e) the host should wait for intb or 300ms before performing any i2c read access. address name b its d escription 0x0a gpoctrl 7:0 g poctrl [7:0] triggers on/off state of gpos when autolight is off 0 : off (ie go to intensityoff ) 1: on (ie go to intensity on ) default is set by spm parameter gpioout pwrup b its of non - gpo pins are ignored. table 31 i2c gpo c ontrol
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 69 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity address name b its d escription 0x0b gpppinid 7:3 reserved, write only ?00000? 2:0 gp p pin identifier defines the gpp pin to which the gppintensity is assigned for the following read/write operations 0x0 = gpp 0 (default) 0x1 = gpp 1 ... 0x7 = gpp 7 gppx refers to pin gpiox configured as gpp table 32 i2c gp p pin identifier address name b its d escri ption 0x0c gppintensity 7 :0 d efines the intensity index of the gpp pin selected in gpppinid 0x00: 0 0x01: 1 ? 0xff: 255 reading returns the intensity index of the gpp pin selected in gpppinid. default value is intensityon or intensityoff depending on gp iooutpwrup. table 33 i2c gpp intensity address name b its d escription 0xb1 softreset 7:0 writing 0xde followed by 0x00 will reset the chip. table 34 i2c s oft r eset
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 70 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.6 spm gateway registers the sx8638 i 2c interface offers two registers for exchanging the spm data with the host. ? spm cfg ? spm baseaddr addre s s name b its d escription 0x0d spmcfg 7:6 00: reserved 5:4 enables i2c spm mode 00: off (default) 01: on 10: reserved 11: reserved 3 d efines r/w dir ection of spm 0: spm write access (default) 1: spm read access 2:0 000: reserved table 35 spm access configuration address name b its d escription 0x0e spm baseaddr 7:0 spm base address (modulo 8). the lowest address is 0x00 (d efault). the highest address is 0x78. table 36 spm base address the exchange of data, read and write, between the host and the spm is always done in bursts of eight bytes. the base address of each burst of eight bytes is a modulo 8 number, starting at 0x00 and ending at 0x78. the registers spm key m sb and spm key l sb are required for nvm programming as described in section 6.7 . address name b its d escription 0xac spmkeymsb 7:0 spm to nvm burn key msb u nl ock requires writing data: 0x62 table 37 spm key msb address name b its d escription 0xad spmkeylsb 7:0 spm to nvm burn key lsb u nlock requires writing data: 0x9d table 38 spm key lsb
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 71 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.6.1 spm w rite sequence the spm write can be done in any mode (active, doze, sleep). writing the spm in sleep is useful to avoid potential transient behaviors. the spm must always be written in blocks of 8 bytes. the sequence is described below: 1. set the i2c in spm mode by writ ing ?01? to spmcfg[5:4] and spm write access by writing ?0? to spm cfg[3]. 2. write the spm base address to spm baseaddr (the base address needs to be a value modulo 8) . 3. write the eight consecutive bytes to i2c address 0, 1, 2, ?7 4. t erminate by writing ?00 0? to spm cfg[5:3 ]. s sa 0 0 x 0 d a 0 x 10 a p a s : start condition sa : slave address a : slave acknowledge b a : nvm base address wdn : write data byte n , n = 0 to 7 p : stop condition ... from master to slave from slave to master s sa 0 0 x 0 e a ba a p a s sa 0 0 x 00 a wd 0 a p a wd 7 s sa 0 0 x 0 d a 0 x 00 a p a 1 ) 2 ) 3 ) 4 ) figure 54 : spm write sequence the complete spm can be written by repeating 16 times the cycles shown in figure 54 using base address es 0x00, 0x08, 0x10, ?, 0x70 , 0x78. between each sequence the host should wait for intb (active/doze) or 30ms in sleep. in active or doze mode, o nce the spm write sequence is actually applied , the intb pin will be asserted and irqsrc[5] set . in sleep mode the spm write can be actual ly applied with a delay of 30ms. th e host clears the interrupt and irqsrc[5] by reading the irqsrc register.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 72 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.6.2 spm read sequence the spm read can be done in any mode (active, doze, sleep). the spm must always be read in blocks of 8 bytes. the sequence i s described below: 1. set the i2c in spm mode by writing ?01? to spmcfg[5:4] and spm read access by writing ?1? to spm cfg[3]. 2. wr ite the spm base address to spm baseaddr (the base address needs to be a value modulo 8). 3. read the eight consecutive bytes from i2c address 0, 1, 2, ?7 4. t erminate by writing ?000? to spm cfg[5:3]. s sa 0 0 x 0 d a 0x18 a p a s, sr : start condition sa : slave address a : slave acknowledge n : not acknowledge (terminates read stream) ba : nvm base address rdn : read data byte n, n = 0 to 7 p : stop condition from master to slave from slave to master s sa 0 0x0e a ba a p a s sa 0 0x0d a 0x00 a p a s sa s sa 0 a 0x00 a sr sa 1 a rd0 a ... rd7 n p 1) 2) 3) 4) figure 55 : spm read sequence the complete spm can be read by repeating 16 times the cycles shown in figure 55 using base address es 0x00, 0x08, 0x10, ?, 0x70, 0x78.
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 73 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.7 nvm burn the content of the spm can be copied permanently (burned) into the nvm to be used as the new default parameters. the burning of the nvm can be done up to three times and must be done only when the spm is completely written with the desired data. the nvm burn must be done in active or doze mode. once the nvm burn process is terminated irqsrc[6] will be set and intb asserted. after a reset the burned nvm parameters will be copied into the sp m. the number of times the nvm has been burned can be monitored by reading nvmcount from the i2c register spmstat[2:0 ]. nvm spm spmstat[2:0] 1 2 3 0 4 qsm figure 56 simplified d iagram nvm count figure 56 show s the simplified diagram of the nvm counter. the sx8638 is delivered with empty nvm and nvmcount set to zero. the spm points to the qsm. each nvm burn will increase the nvmcount . a t the fourth nvm burn the sx8638 switches definitely to the qsm. the burnin g of the spm into the nvm is done by executing a special sequence of four i2c commands. 1. write the data 0x62 to the i2c register i2c key msb . terminate the i2c write by a stop. 2. write the data 0x9d to the i2c register i2c key lsb . terminate the i2c write by a stop. 3. write the data 0xa5 to the i2c register i2c spm baseaddr . terminate the i2c write by a stop. 4. write the data 0x5a to the i2c register i2c spm baseaddr . terminate the i2c write by a stop. this is illustrated in figure 57. s sa 0 0 x 0 e a 0 xa 5 a p a s : start condition sa : slave address a : slave acknowledge p : stop condition from master to slave from slave to master s sa 0 0x0e a 0 x5a a p a 3) 4) s sa 0 0 xac a 0 x62 a p a s sa 0 0 xad a 0 x9d a p a 1) 2) figure 57: nvm burn procedure
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 74 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 6.8 monitor mode monitor mode allows the host to read ?real - time? sensor information (capxraw, capxavg, capxdiff). it is enabled by setting bit 2 of i2c register spmcfg (add ress 0x0d). when enabled, it uses a specific monitor scan period (cf below) and generates an interrupt every time a new full set of data is available (hence every scan period). address name bits description 0xf9 monitor scanperiod 7:0 monitor mode scan p eriod 0x00: reserved 0x01: 15 ms ? 0x0d: 195ms (default) ? 0xff: 255 x 15 ms monitor mode scan period is located at address 0xf9 can be written similarly as spm data (cf. 6.6.1 ) . interrupt is cleared normally by reading i2c r egister irqsrc (address 0x00) but no specific flag is set. capxraw/avg/diff data can be read similarly as spm data (cf. 6.6.2 ). base address ba = 0xb4 is the beginning of the capxdiff data location and data are organized thi s way: 0xb4: cap0diff, msb 0xb5: cap0diff, lsb 0xb6: cap1diff, msb etc... values are coded 16bits signed 2's complement format and updated at each scan period. base address ba = 0x80 is the beginning of the capxraw data location. base address ba = 0x9a is the beginning of the capxavg data location. data should be read before the next interrupt occurs (i.e. within one scan period).
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 75 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 7 a pplication i nformation 7.1 typical application schematic proximity sx 8638 gnd gpio 5 gpio 4 gpio 3 gpio2 gpio1 gnd gpio0 vana resetb gnd gpio7 vdig gpio6 cn cp vdd scl intb sda analog sensor interface micro processor ram rom nvm i2c gpio controller power management clock generation rc pwm led controller bottom plate host d1 d0 d2 d3 d4 d5 d6 d7 cap2 cap3 cap4 cap5 cap6 cap7 cap0 cap1 d0 d1 d2 d3 d4 d5 d6 d7 figure 58 t ypical a pplication
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 76 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 7.2 example of touch+proximity module 7.2.1 overview to demonstrate the proximity sensing feature of the sx863x family, a module has been designed and is illustrated in figure below. touch buttons ( 1 .5cm pitch) proximity sensor module size (white area) : sensors area + sx8633 + connector (min.) bicolor leds (blue, orange) overlay (2mm acrylic glass) figure 59 touch+proximity module overview the touch button controller is running in stand - alone (ie without host) and uses the autolight mode to turn leds on/off accordingly to the touch buttons and proximity sensing status. 7.2.2 o peration module operation can be seen as 5 steps which are described in figure below 1. no finger => no proximity detected => all leds off 2. finger approaches => proximity detected => blue leds turned on 3. button touch => orange led turned on (blue+orange = pink) 4. button r elease => orange led turned off 5. finger removed => no proximity detected => blue leds turned off figure 60 touch+proximity module operation notes: - for better user experience, bicolor leds have been used here but one could decide to design a module with normal unicolor leds. in this case, step 3 above would simply consist in a higher (blue) intensity for the led of the button touched. - for obvious demonstration purposes the overlay used here is transparent but in typical ap plications (tv, monitor, set - top box, etc) the overlay would be opaque enough so that when leds are off (ie no proximity detected) the pcb is not visible to the user. 7.2.3 performance the proximity sensing distance of detection has been measured in these con ditions: - capproxenable = on
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 77 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity - capsensitivity = 7 (max) - capthreshold = 300 - board main supplied and placed vertically ie same orientation as hand/finger - finger pointing center button the results obtained are provided in table below: distance of d etection palm ~10cm finger (natural position) ~6cm orthogonal finger (worst case) ~4cm table 39 proximity sensing distance of detection 7.2.4 schematics figure 61 touch+proximity module schematics
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 78 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 7.2.5 la yout figure 62 touch+proximity module layout - top figure 63 touch+proximity module layout - mid1 figure 64 touch+proximity module layout - mid2 figure 65 touch+proximity module layout - bottom
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 79 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 8 r eferences [1] capacitive touch sensing layout guidelines on www.semtech.com
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 80 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity 9 p ackaging i nformation 9.1 package outline drawing sx8638 is assembled in a mlpq - ut28 package as shown in figure 66 . indicator (laser mark) pin 1 dimensions nom inches n bbb aaa a2 a1 e1 d1 dim l e e d a b min max millimeters min max nom .154 .157 .161 3.90 4.00 4.10 .154 .157 .161 3.90 4.00 4.10 .003 .006 .100 28 .008 .104 .000 .020 (.006) 0.08 0.20 28 .010 .108 0.15 2.55 .024 .001 0.00 0.50 2.75 0.25 2.65 0.02 0.60 (0.152) .004 0.10 2.55 2.65 2.75 0.40 bsc .016 bsc 0.30 .012 .020 .016 0.40 0.50 .108 .104 .100 2 1 seating plane n controlling dimensions are in millimeters (angles in degrees). coplanarity applies to the exposed pad as well as the terminals. 1. 2. notes: - - - - d e a b a1 a aaa c a2 c d1 e1 lxn e/2 e bbb c a b d/2 bxn figure 66 package outline d rawing 9.2 land pattern the land pattern of mlpq - ut28 package, 4 mm x 4 mm is shown in figure 67 . figure 67 land p attern
advanced communications & sensing datasheet revision 8_1 , december 15 ? 2010 semtech corp. www.semtech.com 81 sx8638 low power, capacitive button and slider touch controller (8 sensors) with enhanced led drivers and p roximity contact information ? semtech 2010 all rights reserved. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented i n this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed wit hout notice. no liability will be accepted by the publisher for any consequence of its use. publication thereof does not convey nor imply any license under patent or other industrial or intellectual property rights. semtech assumes no responsibility or lia bility whatsoever for any failure or unexpected operation resulting from misuse, neglect improper installation, repair or improper handling or unusual physical or electrical stress including, but not limited to, exposure to parameters beyond the specified maximum ratings or operation outside the specified range. semtech products are not designed, intended, authorized or warranted to be suitable for use in life - support applications, devices or systems or other critical applications. inclusion of semtech pro ducts in such applications is understood to be undertaken solely at the customer?s own risk. should a customer purchase or use semtech products for any such unauthorized application, the customer shall indemnify and hold semtech and its officers, employees , subsidiaries, affiliates, and distributors harmless against all claims, costs damages and attorney fees which could arise. notice: all referenced brands, product names, service names and trademarks are the property of their respective owners. semte ch corporation advanced communications and sensing products division 200 flynn road, camarillo, ca 93012 phone: (805) 498 - 2111 fax: (805) 498 - 3804

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