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preliminary data this is preliminary information on a new product now in deve lopment or undergoing evaluation. details are subject to change without notice. october 2006 rev 1 1/14 14 LIS302ALK mems motion sensor 3-axis - 2g analog output "piccolo" accelerometer features 3.0v to 3.6v supply voltage ~2mw power consumption 2g full-scale 3 axes acceleration channels ratiometric output voltage embedded self test power down mode 10000g high shock survivability ecopack? rohs and ?green? compliant (see section 5 ) description the LIS302ALK is a miniaturized low-power three-axis linear accelerometer. it includes a sensing element and an ic interface to provide an analog signal to the external world. the sensing element, capable of detecting the acceleration, is manufactured using a dedicated process developed by st to produce motion sensors and actuators in silicon. the ic interface is manufactured using a cmos process that allows to design a dedicated circuit which is trimmed to better match the sensing element characteristics. the device can be operated from 2.16v to 3.6v. the LIS302ALK has a full scale of 2g and it is capable of measuring accelerations over a maximum bandwidth of 2.0khz. the device bandwidth may be reduced by using external capacitances. a self-test capability allows the user to check the functioning of the sensor in the final application without thew need to move or tilt the sensor. the LIS302ALK is available in plastic thin land grid array package (tlga) and it is guaranteed to operate over an extended temperature range from -40c to +85c. the LIS302ALK belongs to a family of products suitable for a variety of applications: ? mobile terminals ? gaming and virtual reality input devices ? free-fall detection for data protection ? antitheft systems and inertial navigation ? appliance and robotics. order codes note: tape & reel parts are compliant to international standard eia-481. lga-14 (3x5x0.9mm) part number temperature range, cpackage packing LIS302ALK -40c to +85c lga-14 tray LIS302ALKtr -40c to +85c lga-14 tape & reel www.st.com
contents LIS302ALK 2/14 contents 1 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 mechanical characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 ic interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3 factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4 application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1 soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2 output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
LIS302ALK block diagram 3/14 1 block diagram figure 1. block diagram 1.1 pin description figure 2. pin connection s/h s/h routx routz reference trimming circuit clock s/h routy charge amplifier mux demux voutx voutz vouty y+ z+ y- z- x+ x- a self test (top view) direction of the detectable accelerations (bottom view) lis302al 1 6 13 8 res res res res st pd vouty voutz gnd res res vdd voutx res y 1 x z
block diagram LIS302ALK 4/14 table 1. pin description pin # pin name function 1 reserved connect to vdd 2 reserved connect to vdd 3 reserved connect to gnd 4 reserved connect to gnd 5 st self test (logic 0: normal mode; logic 1: self-test) 6 pd power down (logic 0: normal mode; logic 1: power-down mode) 7 voutx output voltage x channel 8 vouty output voltage y channel 9 voutz output voltage z channel 10 gnd 0v supply 11 reserved leave unconnected 12 reserved connect to gnd 13 vdd power supply 14 reserved connect to vdd
LIS302ALK mechanical and electrical specifications 5/14 2 mechanical and electrical specifications 2.1 mechanical characteristics. table 2. mechanical characteristics (1) all parameters are specified @ vdd =3.3v, t = 25c unless otherwise noted symbol parameter test condition min. typ. (2) max. unit ar acceleration range (3) 2.0 g so sensitivity (4) 0.415 0.440 0.465 v/g sodr sensitivity change vs temperature delta from +25c 0.01 %/c voff zero-g level (4) t = 25c vdd/2-6% vdd/2 vdd/2+6% v offdr zero-g level change vs temperature delta from +25c 0.5 mg/c nl non linearity (5) best fit straight line 0.5 % fs crossax cross-axis (6) 2% an acceleration noise density vdd=3.3v 200 g/ vt self test output voltage change (7),(8) t = 25c vdd=3.3v x axis +80 +220 mv t = 25c vdd=3.3v y axis +80 +220 mv t = 25c vdd=3.3v z axis +80 +220 mv fres sensing element resonant frequency (9) all axes 2.0 khz top operating temperature range -40 +85 c wh product weight 30 mgram 1. the product is factory calibrated at 3.3v . the operational power supply range is spec ified in table 3. since the device is ratiometric voff, so and vt paramet ers will vary with supply voltage. 2. typical specificat ions are not guaranteed 3. guaranteed by wafer level test and measurement of initial offset and sensitivity 4. zero-g level and sensitivity are ratiometric to supply voltage 5. guaranteed by design 6. contribution to the measuring output of an inclination/acceleration along any perpendicular axis 7. ?self test output voltage change? is defined as vout (vst=logic1) -vout (vst=logic0) 8. ?self test output voltage change? va ries cubically with supply voltage 9. minimum resonance frequency fres=2 .0khz. sensor bandwidth=1/(2* *32k *cload) hz
mechanical and electrical specifications LIS302ALK 6/14 2.2 electrical characteristics table 3. electrical characteristics (1) all parameters are specified @ vdd =3.3v, t=25c unless otherwise noted 1. the product is factory calibrated at 3.3v. symbol parameter test condition min. typ. (2) 2. typical specificat ions are not guaranteed max. unit vdd supply voltage v idd supply current mean value pd pin connected to gnd 0.65 ma iddpdn supply current in power down mode pd pin connected to vdd 1 a vst self test input logic 0 level at vdd=3.3v 0 0.8 v logic 1 level at vdd=3.3v 2.0 vdd v rout output impedance of voutx, vouty, voutz 32 k cload capacitive load drive for voutx, vouty, voutz (3) 3. minimum resonance frequency fres=2 .0khz. device bandwidth=1/(2* *32k *cload) 2.5 nf to n turn-on time at exit from power down mode cload in f 160*cload+0.3 ms to p operating temperature range -40 +85 c
LIS302ALK mechanical and electrical specifications 7/14 2.3 absolute maximum ratings stresses above those listed as ?absolute ma ximum ratings? may cause permanent damage to the device. this is a stress rating only and functional operation of the device under these conditions is not implied. exposure to maximum rating conditions for extended periods may affect device reliability. 2.4 terminology sensitivity describes the gain of the sensor and can be determined by applying 1g acceleration to it. as the sensor can measur e dc accelerations this can be done easily by pointing the axis of interest towards the center of the earth, note the output value, rotate the sensor by 180 degrees (point to the sky) and note the output value again thus applying 1g acceleration to the sensor. subtracting the larger output value from the smaller one and dividing the result by 2 will give the actual se nsitivity of the sensor. this value changes very little over temperature (see sensitivity change vs. temperature) and also very little over time. the sensitivity tolerance describes the range of sensitivities of a large population of sensors. zero-g level describes the actual output signal if there is no acceleration present. a sensor in a steady state on a horizontal surface will me asure 0g in x axis and 0g in y axis whereas the z axis will measure +1g. the output is ideally for a 3.3v powered sensor vdd/2 = 1650mv. a deviation from ideal 0-g level (1650mv in this case) is called zero-g offset. offset of precise mems sensors is to some extend a result of stress to the sensor and therefore the offset can slightly change after mountin g the sensor onto a printed circuit board or exposing it to extensive mechanical stress. offset changes little over temperature - see ?zero-g level change vs. temperature? - the zero-g level of an individual sensor is very stable table 4. absolute maximum ratings symbol ratings maximum value unit vdd supply voltage -0.3 to 6 v vin input voltage on any control pin (pd, st) -0.3 to vdd +0.3 v a pow acceleration (any axis, powered, vdd=3.3v) 3000g for 0.5 ms 10000g for 0.1 ms a unp acceleration (any axis, not powered) 3000g for 0.5 ms 10000g for 0.1 ms t stg storage temperature range -40 to +150 c esd electrostatic discharge protection 2 (hbm) kv 1.5 (cdm) kv 200 (mm) v this is a mechanical shock sensitive device, improper handling can cause permanent damages to the part this is an esd sensitive device, improper handling can cause permanent damages to the part
mechanical and electrical specifications LIS302ALK 8/14 over lifetime. the zero-g level tolerance describes the range of zero-g levels of a population of sensors. self test allows to check the sensor functionality without moving it. the self test function is off when the st pin is connected to gnd. when the st pin is tied at vdd an actuation force is applied to the sensor, simulating a definite input acceleration. in this case the sensor outputs will exhibit a voltage change in their dc levels which is related to the selected full scale and depending on the supply voltage through the device sensitivity. when st is activated, the device output level is given by the algebraic sum of the signals produced by the acceleration acting on the sensor and by th e electrostatic test-force. if the output signals change within the amplitude specified inside table 2, than the sensor is working properly and the parameters of the interface chip are within the defined specification. output impedance describes the resistor inside the output stage of each channel. this resistor is part of a filter consisting of an ex ternal capacitor of at least 2.5nf and the internal resistor. due to the resistor level, only small inexpensive external capacitors are needed to generate low corner frequencies. when interfacing with an adc it is important to use high input impedance input circuitries to avoid measurement errors. note that the minimum load capacitance forms a corner frequency close to the resonance frequency of the sensor. in general the smallest possible bandwidth for a pa rticular application should be chosen to get the best results.
LIS302ALK functionality 9/14 3 functionality the LIS302ALK is an ?piccolo? low-power, analog output three-axis linear accelerometer packaged in a lga package. the complete device includes a sensing element and an ic interface able to take the information from the sensing element and to provide an analog signal to the external world. 3.1 sensing element a proprietary process is used to create a surface micro-machined accelerometer. the technology allows to carry out suspended s ilicon structures which are attached to the substrate in a few points called anchors and are free to move in the direction of the sensed acceleration. to be compatible with the traditional packaging techniques a cap is placed on top of the sensing element to avoid blocking the moving parts during the moulding phase of the plastic encapsulation. when an acceleration is applied to the sensor the proof mass displaces from its nominal position, causing an imbalance in the capacit ive half-bridge. this imbalance is measured using charge integration in response to a voltage pulse applied to the sense capacitor. at steady state the nominal value of the capacitors are few pf and when an acceleration is applied the maximum variation of the capacitive load is in ff range. 3.2 ic interface the complete signal processing uses a fully differential structure, while the final stage converts the differential signal into a single-ended one to be compatible with the external world. the first stage is a low-noise capacitive amplifier that implements a correlated double sampling (cds) at its output to cancel the offset and the 1/f noise. the produced signal is then sent to three different s&hs, one for each channel, and made available to the outside. all the analog parameters (output offset voltage and sensitivity) are ratiometric to the voltage supply. increasing or de creasing the voltage supply, t he sensitivity and the offset will increase or decrease linearly. the feature provides the cancellation of the error related to the voltage supply along an analog to digital conversion chain. 3.3 factory calibration the ic interface is factory calibrated for sensitivity (so) and zero-g level (voff). the trimming values are stored inside the device in a non volatile structure. any time the device is turned on, the trimming parameters are downloaded into the registers to be employed during the normal operation. this allows the user to employ the device without further calibration.
application hints LIS302ALK 10/14 4 application hints figure 3. LIS302ALK electrical connection power supply decoupling capacitors (100nf ceramic or polyester + 10f aluminum) should be placed as near as possible to the device (common design practice). the LIS302ALK allows to band limit voutx, vouty and voutz through the use of external capacitors. the recommended frequency range spans from dc up to 2.0khz. capacitors must be added at output pins to implement low-pass filtering for antialiasing and noise reduction. the equation for the cut-off frequency (f t ) of the external filters is: taking into account that the internal filtering resistor (r out ) has a nominal value equal to 32k , the equation for the external filter cut-off frequency may be simplified as follows: the tolerance of the internal resistor can vary typically of 20% within its nominal value of 32k ; thus the cut-off frequency will vary accord ingly. a minimum capacitance of 2.5nf for c load (x, y, z) is required in any case. direction of the detectable accelerations y 1 x z digital signals vout x LIS302ALK vout y cload y cload x (top view) optional optional lis302al 1 st pd vout z optional cload z 6 8 13 100nf 10 f gnd gnd vdd gnd vdd pin 1 indicator gnd gnd f t 1 2 r out c load xyz ,, () ?? --------------------------------------------------------------- - = f t 5 f c load xyz ,, () ----------------------------------- hz [] =
LIS302ALK application hints 11/14 4.1 soldering information the lga package is compliant with the ecopack, rohs and ?green? standard.it is qualified for soldering heat resistan ce according to jedec j-std-020c. pin1 indicator is electrically connected to pin 1. leave pin 1 indicator unconnected during soldering. land pattern and soldering recommendations are available at www.st.com/mems . 4.2 output response vs. orientation figure 4. output response vs. orientation note: figure 4 refers to LIS302ALK powered at 3.3v. table 5. filter capacitor selection, c load (x,y,z) cut-off frequency capacitor value 1 hz 5 f 10 hz 0.5 f 20 hz 250nf 50 hz 100nf 100 hz 50nf 200 hz 25nf 500 hz 10nf earth?s surface x=1.65v (0g) y=1.65v (0g) z=2.13v (+1g) x=1.65v (0g) y=1.65v (0g) z=1.17v (-1g) top view x=1.17v (-1g) y=1.65v (0g) x=2.13v (+1g) y=1.65v (0g) x=1.65v (0g) y=1.17v (-1g) x=1.65v (0g) y=2.13v (+1g) z=1.65v (0g) z=1.65v (0g) z=1.65v (0g) z=1.65v (0g) to p bottom to p bottom
package information LIS302ALK 12/14 5 package information in order to meet environmental requirements, st offers these devices in ecopack? packages. these packages have a lead-free second level interconnect. the category of second level interconnect is marked on the package and on the inner box label, in compliance with jedec standard jesd97. the maximum ratings related to soldering conditions are also marked on the inner box label. ecopack is an st trademark. ecopack specifications are available at: www.st.com. figure 5. lga 14: mechanical data & package dimensions outline and mechanical data dim. mm inch min. typ. max. min. typ. max. a1 0.920 1.000 0.0362 0.0394 a2 0.700 0.0275 a3 0.180 0.220 0.260 0.0071 0.0087 0.0102 d1 2.850 3.000 3.150 0.1122 0.1181 0.1240 e1 4.850 5.000 5.150 0.1909 0.1968 0.2027 e 0.800 0.0315 d 0.300 0.0118 l1 4.000 0.1575 n 1.360 0.0535 n1 1.200 0.0472 p1 0.965 0.975 0.985 0.0380 0.0384 0.0386 p2 0.640 0.650 0.660 0.0252 0.0256 0.0260 t1 0.750 0.800 0.850 0.0295 0.0315 0.0335 t2 0.450 0.500 0.550 0.0177 0.0197 0.0217 r 1.200 1.600 0.0472 0.0630 h 0.150 0.0059 k 0.050 0.0020 i 0.100 0.0039 s 0.100 0.0039 lga14 (3x5x0.92mm) pitch 0.8mm l and g rid a rray package 7773587 c
LIS302ALK revision history 13/14 6 revision history table 6. document revision history date revision changes 30-oct-2006 1 initial release.
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