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? ? SI4022 universal ism band fsk transmitter description silicon labs? SI4022 is a single ch ip, low power, multi-channel fsk transmitter designed for use in applications requiring fcc or etsi conformance for unlicensed use in th e bands at 868 and 915 mhz. used in conjunction with integration?s fsk receivers, it is a flexible, low cost, and highly integrated solution that does not require production alignments. all required rf functions are integrated. only an external crystal and bypass filtering is needed for operation. the transmitter has a completely integrated pll for easy rf design, and its rapid settling time allows for fast frequency-hopping, bypassing multipath fading and interference to achieve robust wireless links. the pll?s high resolution allows the usage of multiple channels in any of the bands. in addition, highly stable and accurate fsk modulation is accomplished by direct closed-loop modulation wi th bit rates up to 115.2 kbps. the integrated power amplifier of the transmitter has an open-collector differential output and can directly dr ive a loop antenna with programmable output level, no additional matching network is required. an automatic antenna tuning circuit is built in to avoid both costly trimming procedures and de-tuning due to the ?hand effect?. for battery-operated applications the device supports various power saving modes with wake-up interrupt genera tion options based on a low battery voltage detector and a sleep timer. several additional features ease system design. power-on reset and clock signals are provided to the microcontroller. an on-chip baud rate generator and a da ta fifo are availabl e. the transmitter is programmed and controlled via an spi compatible interface. features ? fully integrated (low bom, easy design-in) ? no alignment required in production ? fast settling, programmable, high-resolution pll ? fast frequency hopping capability ? stable and accurate fsk modulation with programmable deviation ? programmable pll loop bandwidth ? direct loop antenna drive ? automatic antenna tuning circuit ? programmable output power level ? spi bus for interfacing with microcontroller ? clock and reset signals for microcontroller ? 64 bit tx data fifo ? integrated programmable crystal load capacitor ? standard 10 mhz crystal reference ? power-saving modes ? multiple event handling options for wake-up activation ? wake-up timer ? low battery detection ? 2.2 to 3.8 v supply voltage ? low power consumption ? low standby current (typ. 0.3 a) typical applications ? remote control ? home security and alarm ? wireless keyboard/mouse and other pc peripherals ? toy control ? remote keyless entry ? tire pressure monitoring ? telemetry ? personal/patient data logging ? remote automatic meter reading 1ia4 222-ds rev 1.1r 030 this document refers to SI4022-ic rev a0. see www.silabs.com/integration for any applicable errata. see back page for ordering information. pin assignment sdi 1 16 fsk sck nsel sdo 2 3 15 vdd 14 4 13 vss_b rf02 nirq 5 12 rf01 clk 6 11 vss_a vrefo 7 10 nres vss_d 8 9 xtl / ref synthesizer controller low battery detect wake -up timer functional block diagram 13 rf02 xtl 9 12 rf01 clock frequency load cap level 6 clk low bat 5 nirq treshold 4 sdo vdd 15 vss_a 11 timeout vdd_b 14 period vss_d 8 1 sdi 2 sck 3 nsel 16 fsk vref o 7 1 0 nres SI4022 crystal oscillator reference ?
? ? si4 i ? 022 detailed feature-level description the SI4022 fsk transmitter is designed to cover the unlicensed frequency bands at 868, and 915 mhz. the device facilitates compliance with fcc an d etsi requirements. pll the programmable pll synthesizer determines the operating frequency, while preserving accuracy based on the on-chip crystal-controlled reference oscill ator. the pll?s high resolution allows the usage of multiple channels in any of the bands. the fsk deviation is selectable (from 20 to 160 khz with 20 khz increments) to accommodate vari ous bandwidth, data rate and crystal tolerance requirements, an d it is also highly accurate due to the direct closed-loop modulation of the pll. the transmitted digital data can be sent asynchronously through the fsk pin or over the control interface using the appropriate command. the rf vco in the pll performs automatic calibration, which requires only a few microseconds . to ensure proper operation in the programmed frequency band , the rf vco is automatically calibrated upon activati on of the synthesizer. rf power amplifier (pa) the power amplifier has an open-collector differential output and can directly drive a loop antenna with a programmable output power level. an automatic antenna tuning circuit is built in to avoid costly trimming procedures and the so-called ?hand effect.? crystal oscillator and microcontroller clock output the chip has a single-pin crystal oscillator circuit, which provides a 10 mhz reference signal for the pll. to reduce external parts and simplify design, the crystal load capacitor is internal and programmable. guidelines for se lecting the appropriate crystal can be found later in this datasheet. the transmitter can supply the clock signal for the microcontroller, so accurate timing is possible without the need for a second crystal. in normal operation it is divided from the reference 10 mhz. during sleep mode a low frequency (typical 32 khz) output clock signal can be switched on. when the microcontroller turns the crystal oscillator off by clearing the appropriate bit using the power management command, the chip provides a certain number (default is 128) of further clock pulses (?clock tail?) for the microcontroller to let it go to idle or sleep mode. low battery voltage detector the low battery detector circuit monitors periodically (typ. 8 ms) the supply voltage and generates an interrupt if it falls below a programmable threshold level. wake-up timer the wake-up timer has very low current consumption (4 a max) and can be programmed from 1 ms to several hours. it calibrates itself to the crysta l oscillator at every startup and then at every 40 seconds with an accuracy of 0.5%. when the crystal oscillator is switched off, the calibration circuit switches it back on only long enough for a quick calibration (a few milliseconds) to facilitate accu rate wake-up timing. the periodic autocalibration feature can be turned off. event handling in order to minimize current consumption, the transmitter supports the sleep mode. switch ing between the various modes is controlled by the appropriate bits in the power management command (page 11). SI4022 generates an interrupt sign al on several events (wake- up timer timeout, low supply voltage detection, on-chip fifo almost empty). this signal can be used to wake up the microcontroller, effectively reducing the period the microcontroller has to be active. the cause of the interrupt can be read out from the receiver by the microcontroller through the sdo pin. interface and controller an spi compatible serial interface lets the user select the frequency band, center frequency of the synthesizer, and the output power. division ratio for the microcontroller clock, wake- up timer period, and low supply voltage detector threshold are also programmable. any of th ese auxiliary functions can be disabled when not needed. all para meters are set to default after power-on; the programmed values are retained during sleep mode. the interface supports the read-out of a status register, providing detailed information about the status of the transmitter.
SI4022 ? ? ? pin definition pin type key: d=digital, a=analog, s=su pply, i=input, o=output, io=input/output sdi sck nsel sdo nirq clk vrefo vss_d fsk vdd vss_b rf02 rf01 vss_a nres xtl / ref pin name function type description 1 sdi sdi di serial control / data input 2 sck sck di serial interface clock input 3 nsel nsel di chip (interface) select input (active low) 4 sdo sdo do serial status data output 5 nirq nirq do interrupt request output (active low) 6 clk clk do clock output for the microcontroller 7 vrefo vrefo ao voltage reference output 8 vss_d vss_d s negative supply voltage (digital) 9 xtl / ref xtl aio crystal connection (other terminal of crystal to vss) ref di external reference input 10 nres nres do reset output (active low) 11 vss_a vss_a s negative supply voltage (analog) 12 rfo1 rfo1 ao rf differential signal output (open collector) 13 rfo2 rfo2 ao rf differential signal output (open collector) 14 vss_b vss_b s negative supply voltage (bulk) 15 vdd vdd s positive supply voltage 16 fsk fsk di data input for asynchronous modulation 1 ? 16 2 ? 15 3 ? 14 4 ia4222 13 5 ? 12 6 ? 11 7 ? 10 8 ? 9
SI4022 ? ? ? ss general device specification all voltages are referenced to v , the potential on the ground reference pin vss. absolute maximum ratings (non-operating) symbol paramete r min ma x units v dd positive supply voltage -0.5 6.0 v v in voltage on any pin -0.5 v dd +0.5 v i in input current into any pin except vdd and vss -25 25 ma esd electrostatic discharge with human body model ? 1000 v t st storage temperature -55 125 o c t ld lead temperature (soldering, max 10 s) ? 260 o c recommended operating range symbol parameter min max units v dd positive supply voltage 2.2 3.8 v t op ambient operating temperature -40 +85 o c electrical specification (min/max values are valid over the whole re commended operating range, typ conditions: t = 27 o c; v = 2.7 v) dc characteristics symbol parameter conditions/notes min t yp max units i dd,tx0 supply current 868 mhz band, p out = 0dbm 915 mhz band, p out = 0dbm ? 14 15 ? ma i dd,txmax supply current 868 mhz band, p out = p max 915 mhz band, p out = p max ? 23 24 ? ma i pd standby current (note 1) all blocks disabled ? 1 ? a i lb low battery voltage detector and wake-up timer current ??? 5 a i x idle current crystal oscillator is on ? 0.5 ? ma v lb low battery detection threshold programmable in 0.1 v steps 2.0 ? 3.5 v v lba low battery detection accuracy ?? 0.05 ? v v por v dd threshold required to generate a por ?? 1.5 ? v v por,hyst por hysteresis larger glithches on the v dd generate a por even above the threshold v por ? 0.6 ? v sr vdd v dd slew rate for proper por generation 0.1 ?? v/ms note 1: using a cr2032 battery (225 mah capa city), the expected battery life is greater than 2 year s using a 60-second wake-up period for sending 100 bytes packets in length at 19.2 kb ps with +6 dbm output power in the 915 mhz band. op dd = v oc
SI4022 ? ? ? dc characteristics (continued) symbol paramete r conditions/notes min t yp ma x units v il digital input low level ??? 0.3*v dd v v ih digital input high level ? 0.7*v dd ?? v i il digital input current v il = 0 v -1 ? 1 a i ih digital input current v ih = v dd , v dd = 3.8 v -1 ? 1 a v ol digital output low level i ol = 2 ma ?? 0.4 v v oh digital output high level i oh = -2 ma v dd -0.4 ?? v ac characteristics symbol paramete r conditions/notes min t yp ma x units f lo transmitter frequency 868 mhz band, 20 khz resolution 915 mhz band, 20 khz resolution 801.92 881.92 ? 878.06 958.06 mhz f ref pll reference frequency (note 1) 9 10 11 mhz f res pll frequency resolution ?? 20 ? khz t lock pll lock time frequency error < 1khz after 1 mhz step ? 30 ? s t sp pll startup time initial calibration after power-up with running crystal oscillator ?? 500 s c xl crystal load capacitance, see crystal selection guide programmable in 0.5 pf steps, tolerance +/- 10% 8.5 ? 16 pf t por internal por pulse width (note 2) after v dd has reached 90% of final value ? 50 100 ms t sx crystal oscillator startup time crystal esr < 100 ? ? ? 2 5 ms t pbt wake-up timer clock period calibrated every 40 seconds (note 3) 0.995 1 1.005 ms t wake-up programmable wake-up time ? 1 ? 8.4*10 6 ms note 1: using anything but a 10 mhz crystal is allowed bu t not recommended because all crys tal-referred timi ng and frequency parameters will change accordingly. note 2: no command are accepted by the chip during this period. note 3: autocalibration can be turned off.
SI4022 ? ? ? ac characteristics (continued) symbol paramete r conditions/notes min t yp ma x units br fsk bit rate (note 4) ?? 115.2 kbps i out open collector output current adjustable in 8 steps 0.5 ? 6 ma p max available output power with optimal antenna impedance (note 5) ? 6 ? dbm p out typical output power adjustable in 8 steps (3 db/step) p max - 21 ? p max dbm p sp spurious emission out of band, eirp (note 6) ?? -52 dbm c out output capacitance set by the automatic antenna tuning circuit 1.6 2.2 2.8 pf q out quality factor of the output capacitance ? 16 18 22 ? l out output phase noise 100 khz from carrier 1 mhz from carrier (note 4) ? -85 -105 ? dbc/hz c in, d digital input capacitance ??? 2 pf t r, f digital output rise/fall time 15 pf pure capacitive load ?? 10 ns t r, f ,ckout clock output rise/fall time 10 pf pure capacitive load ?? 15 ns f ckout, slow slow clock frequency tolerance +/- 1 khz ? 32 ? khz setting (bw1, bw0) max. datarate [kbps] phase noise a t 1 mhz offset [dbc/hz] pll bandwidth 00 19.2 -112 15 khz 01 38.4 -110 30 khz 10 64 -107 60 khz (por default) 11 115.2 -102 120 khz band y antenna [s] z antenna [ ? ] l antenna [nh] 868 mhz 1.35e-3 ? j1.2e-2 9 + j82 15.2 915 mhz 1.45e-3 ? j1.3e-2 8.7 + j77 13.6 note 4: the maximum fsk bitrate and the output ph ase noise are dependent on the pll settings (with the extended features command ). note 5: optimal antenna / admittance / inductance for the SI4022 note 6: with selective resonant antennas (see: application notes available from http://www.silabs.com/integration).
SI4022 ? ? ? typical performance data phase noise measurements in the 868 mhz ism band 50% charge pump current setting (ref. level: -60 dbc/hz, 10 db/div) 100, 50, 33% charge pump current settings (ref. level: -70 dbc/hz, 5 db/div) 11:52:47 may 5, 2005 phase noise l 13:30:49 may 5, 2005 phase noise l carrier power -11.11 dbm atten 0.00 db mkr4 5.00800 mhz carrier power -11.03 dbm atten 1.1 db mkr1 1.00000 mhz ref -60.00dbc/hz 10.00 db/ 1 -115.65 dbc/hz ref -70.00dbc/hz 5.00 db/ -101.95 dbc/hz 2 4 10 khz frequency offset 10 mhz 10 khz frequency offset 10 mhz marker trace type x axis value marker trace type x axis value 1 2 spot freq 2 2 spot freq 3 2 spot freq 4 2 spot freq 10 khz 151 khz 1 mhz 5.008 mhz -76.65 dbc/hz -86.95 dbc/hz -107.11 dbc/hz -115.65 dbc/hz 1 1 spot freq 2 2 spot freq 3 3 spot freq 1 mhz 1 mhz 1 mhz -101.95 dbc/hz -107.05 dbc/hz -109.98 dbc/hz unmodulated rf spectrum the output spectrum is measured at different frequencies. th e output is loaded with 50 ohm through a matching network. at 868 mhz at 915 mhz 10:26:50 may 5, 2005 l ref 0 dbm atten 10 db samp mkr1 868.0010 mhz -12.2 dbm 10:34:57 may 5, 2005 l ref 0 dbm atten 10 db samp mkr1 915.0020 mhz -14.09 dbm log 1 10 db/ vavg 100 w1 s2 s3 fc aa log 10 db/ vavg 100 w1 s2 s3 fc aa center 868 mhz ? span 2 mhz ? center 915 mhz ? span 2 mhz res bw 10 khz v bw 10 khz sweep 40.74 ms (2001 pts) res bw 10 khz vbw 10 khz sweep 40.74 ms (2001 pts) 1 2 ?? ?? ?? ?? ?? ?? ?? ?? ?? ??
SI4022 ? ? ? v g s2 fc a a at 868 mhz with 180 khz deviation at 9.6 kbps 11:14:40 may 5, 2005 l ref 0 dbm atten 10 db samp log 10 db/ va 100 w1 s3 center 868 mhz res bw 10 khz vbw 10 khz span 2 mhz sweep 40.74 ms (2001 pts) antenna tuning characteristics 750?970 mhz the antenna tuning characteristics was reco rded in ?max-hold? state of the spectrum analyzer. during the measurement, the transmitters were forced to change frequencies by forcing an ex ternal reference signal to the xtl pin. while the carrier was ch anging the antenna tuning circuit switched trough all the available stat es of the tuning circuit. the graph clearly demonstrates that while the complete output circuit had about a 40 mhz bandwidth, the tuning allows operating in a 220 mhz band. in other words the tuning circuit can compensate for 25% variation in the resonant frequency due to any process or manufacturing spread. ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
SI4022 ? ? ? control interface commands to the transmitters are sent serial ly. data bits on pin sdi are shifted into the device upon the rising edge of the cl ock on pin sck whenever the chip select pin nsel is low. when the nsel signal is high, it initializes the serial interface. the number of bits sent is an integer multiple of 8 (except for the transmitter fifo write command ). all commands consist of a command code, followed by a varying number of parameter or data bits. all da ta are sent msb first (e.g. bit 15 for a 16-bit command). bits ha ving no influence (don?t care) are indicated with x. the power on rese t (por) circuit sets default values in all control and command registers. timing specification symbol paramete r minimum value [ns] t ch clock high time 25 t cl clock low time 25 t ss select setup time (nsel falling edge to sck rising edge) 10 t sh select hold time (sck falling edge to nsel rising edge) 10 t shi select high time 25 t ds data setup time (sdi transition to sck rising edge) 5 t dh data hold time (sck rising edge to sdi transition) 5 t od data delay time 10 timing diagram t ss t shi nsel t ch t cl t od t sh sc k t ds t dh sdi bit15 bit14 bit13 bit8 bit7 bit1 bit0 sdo bit15 bit14 bit13 bit8 bit7 bit1 bit0
SI4022 ? ? ? f 0 control commands control word related parameters/functions configuration setting command frequency band and deviation, output power, crystal oscillator load capacitance frequency setting command frequency of the local oscillator power managament command crystal oscillator, synthesizer , power amplifier, low battery detector, wake-up timer, clock output buffer transmitter fifo write command transmitter fifo write fifo setting command fifo functions data rate command bit rate low battery and microcontroller clock divider command lbd voltage threshold and microcontroller clock division ratio wake-up timer command wake-up time period extended wake-up timer command wake-up time period finer adjustment extended features command low frequency output clock, wake-up timer extra functions status register read command transmitter status read n n no o ot t te e e: in the following tables the por column shows the default values of the command registers after power-on. configuration setting command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 0 0 1 bs p2 p1 p0 x3 x2 x1 x0 ms m2 m1 m0 9082h the resulting output frequency can be calculated as: the output power is given in the table as where: out ? (-1) sign * (m + 1) * (20 khz) relative to the maximum available power, which depends on the actual antenna impedance. (see: antenna application note available from http://www.silabs.com/integration). is the channel center frequency (see the next command) m is the three bit binary number < m2 : m0> sign = ( ms ) xor (fsk input) x3 x2 x1 x0 crystal load capacitance [pf] 0 0 0 0 8.5 0 0 0 1 9.0 0 0 1 0 9.5 0 0 1 1 10.0 ?? ?. 1 1 1 0 15.5 1 1 1 1 16.0 bs frequency band [mhz] 0 868 1 915 f 0 = f p2 p1 p0 output power [dbm] 0 0 0 0 0 0 1 -3 0 1 0 -6 0 1 1 -9 1 0 0 -12 1 0 1 -15 1 1 0 -18 1 1 1 -21
SI4022 ? ? ? 0 frequency setting command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 0 1 0 f11 f10 f9 f8 f7 f6 f5 f4 f3 f2 f1 f0 ad57h the 12-bit parameter of the frequency setting command has the value f. the value f should be in the range of 96 and 3903. when f is out of range, the previous value is kept. the synthesizer the constant c is determined by the selected band as: center frequency f can be calculated as: = 8 * 10 mhz * (c + f/4000) power management command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 1 0 0 0 0 0 0 0 0 ex es etr eb et dc c002h bit 5 < ex >: enables the the crystal oscillator. bit 4 < es >: enables the synthesizer. bit 3 < etr >: enables the power amplifier. if the ex and es bit is not set, it switches on the crystal oscillator and the synthesizer as well. in fifo mode (bit fe is set in the fifo setting command ) setting this bit will roll out the content of the fifo. bit 2 < eb >: enables the low battery detector. bit 1 < et >: enables the wake-up timer. bit 0 < dc >: disables the clock output buffer. n n no o ot t te e e: if faster operation is needed, then leave ex and es bit set to ?1? and toggle only the etr bit. power saving modes the different operating modes of the chip depend on the following control bits: operating mode eb or e t e s et r e x active (transmit) x x 1 x idle x 0 0 1 sleep 1 0 0 0 standby 0 0 0 0 transmitter fifo write command bit 7 6 5 4 3 2 1 0 por ? 1 1 0 0 0 1 1 0 - with this command, the controller can write databits to the transmitter fifo. bit (fe) must be set in the fifo setting command. f 0 band [mhz] c 868 10 915 11
SI4022 ? ? ? nsel p o w e r m a n a g e m e n t c o m m a n d c 0 h 3 8 h sc k instruction sdi internal operations ex, es, etr = 1 xtal osc staus synthesize r / pll / pa status s y nthesize r on, pll locked, pa read y to transmit fsk d o n ' t c a r e t x d a t a note: * see page 5 for the timing values transmitter fifo register write data transmit sequence through the fsk pin it is possible to transmit data without the fifo by using the fs k input pin. in that case the power amplifier should be enabled first with the power management comand. ? t sx * ? xtal osc. stable ? t sp * n n no o ot t te e e : ? if the crystal oscillator was formerly switched off ( ex =0), the internal oscillator needs t sx time, to switch on. the actual value depends on the type of quartz crystal used. ? if the synthesizer was formerly switched off ( es =0), the internal pll needs t sp startup time. valid data can be transmitted only when the internal locking process is finished. nsel 0 1 2 3 4 5 6 7 0 1 2 3 4 5 n-2 n-1 sc k instruction fillin g u p fifo sdi n data bits
SI4022 ? ? ? lb lb fifo setting command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 1 0 0 1 1 1 0 fe 0 f5 f4 f3 f2 f1 f0 ce00h bit 7 < fe >: enables the 64 bit transmit fifo. resetting this bit clears the contents of the fifo. bit 5-0 < f5 : f0 >: fifo it level. the fifo generates it when number of the remaining data bits in the fifo reaches this leve data rate command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 1 0 0 1 0 0 0 cs r6 r5 r4 r3 r2 r1 r0 c813h the bit rate of the transmitted data stream is determined by the 7-bit value r (bits r6 to r0 ) and the 1 bit cs . br = 10 mhz / 29 / (r+1) / ( 1 + cs *7) in the receiver set r according the next function: r= (10 mhz / 29 /( 1 + cs *7)/ br) ? 1 apart from setting custom values, the standard bit rates from 600 bps to 115.2 kbps can be approximated with small error. low battery and microcontroller clock divider command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 1 0 0 0 0 1 0 d2 d1 d0 elfc t3 t2 t1 t0 c213h the 4-bit value t of t3 - t0 determines the threshold voltage of the threshold voltage v v = 2.0 v + t * 0.1 v of the detector: bit 4 < elfc >: enables low frequency (32 khz) microc ontroller output clock during sleep mode. clock divider configuration (valid only if the crystal oscillator is on): d2 d1 d0 clock output frequency [mhz] 0 0 0 1 0 0 1 1.25 0 1 0 1.66 0 1 1 2 1 0 0 2.5 1 0 1 3.33 1 1 0 5 1 1 1 10 wake-up timer command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 1 1 0 r3 r2 r1 r0 m7 m6 m5 m4 m3 m2 m1 m0 e196h the wake-up time period can be calculated by m < m13 : m0 > , r < r3 : r0 > and d < d1 : d0 >: wake-up = m * 2 r-d ms t
SI4022 ? ? ? n n no o ot t te e e:? the wake-up timer generates interrupts continuously at the programmed interval while the et bit is set. extended wake-up timer command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 1 0 0 0 0 1 1 d1 d0 m13 m12 m11 m10 m9 m8 c300h these bits can be used for further fine adjustment of the wa ke-up timer. the explanation of the bits can be found above. ? ? extended features command: bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 1 0 1 1 0 0 0 0 exlp ctls 0 dcal bw1 bw0 dsfi ewi b0cah bit 7 < exlp >: enables low power mode for the crystal oscillator. bit 6 < ctls >: clock tail selection bit. setting this bit selects 512 cycle long clock tail instead of the default 128. bit 4 < dcal >: disables the wake-u p timer autocalibration. bit 3-2 < bw1:bw0 >: select the bandwidth of the pll. bw1 bw0 pll bandwidth 0 0 15 khz 0 1 30 khz 1 0 60 khz 1 1 120 khz bit 1 < dsfi >: disables autosleep on fifo interrupt if set to 1. bit 0 < ewi >: enables the automatic wake-up on any interrupt event. status register read command bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 por ? 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - with this command, it is possible to read the status register of the chip through the sdo pin. ffit the number of data bits in the fi fo has gone below the preprogrammed limit ffem fifo is empty ffov fifo overflow lbd low battery detect, the power supply voltage is below the preprogrammed limit wk-up wake-up timer overflow por power-on reset
SI4022 ? ? ? status register read sequence nsel 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 sck sdi status out sdo ffit ffem ffov lbd wk-up por
SI4022 ? ? ? x dual clock output when the chip is switched into idle mode, the 10 mhz crystal os cillator starts. after oscillatio n ramp-up a 1 mhz clock signal is available on the clk pin. this (fast) clock freque ncy can be reprogrammed during operation with the low battery and microcontroller clock divider command (page13). during startup and in sleep or standby mode (crystal oscillator disabled), the clk output is pulled to logic low. on the same pin a low frequency cloc k signal can be obtained if the elfc bit is set in the low battery and microcontroller clock divider command . the clock frequency is 32 khz which is derived from the low-power rc oscillator of the wake-up timer. in order to use this slow clock the wake-up timer should be enabled by setting the et bit in the power management command (page 11) even if the wake- up timer itself is not used. slow clock feature can be enabled by enteri ng into sleep mode (page 11). driving the output will increase the sleep mode supply current. actual worst-case value can be determined when the exac t load and min/max operating conditions are defined. after powe r- on reset the chip goes into sleep mode and th e slow frequency clock appears on the clk pin. switching back into fast clock mode can be done by setting the ex or etr bits in the approriate commands. it is important to leave bit dc in the power management command at its default state (0) otherwise there will be no clock signal on the clk pin. switching between the fast and slow clock modes is glitch-free in a sense that either state of the clock lasts for at least a h alf cycle of the fast clock. during switching the cl ock can be logic low once for an intermedia te period i.e. for any time between the ha lf cycle of the fast and the slow clock. the clock switching synchronization circuit detects the falling edges of the clocks. one consequence is a latency of 0 to t slow fast from the occurrence of a clock change request (entering into sleep mode or interrupt) until the beginning of the intermediate length (t ) half cycle. the other is that both clocks should be up and running for the change to occur. changing from fast to slow clock, it is automatical ly ensured by entering into the sleep mode in the appropriate way provided that the wake-up timer is continouosly enabled. as the crystal osc illator is normally stopped while the slow clock is used, when changing back to fast clock the crystal oscillator startup time has to pass first before the above mentioned latency period starts. the startup condition is detected internally, so no software timing is necessary. wake-up timer calibration by default the wake-up timer is calibrated each time it is enabled by setting the et bit in the power management command . after timeout the timer can be stopped by resetting this bit otherwise it operates continuously. if the timer is programmed to run fo r longer periods, at approximately every 40 seconds it performs additional self-calibration. this feature can be disabled to avoid sudden changes in the actu al wake-up time period. a suitable software algorithm can then compensate for the gradual shift caused by temperature change. bit dcal in the extended features command (page 14) controls the automatic calibration feat ure. it is reset to 0 at power-on and the automatic calibration is enabled. this is necessary to compen sate for process tolerances. after one calibration cycle further (re)calibration can be disabled by setting this bit to 1. t slow clock periods are not to scale slow clock fast clock output 0.5 * t fast < t x < 0.5 * t slow t x t fast + t
SI4022 ? ? ? matching network for a 50 ohm single ended output matching network schematic rx-tx alignment procedures rx-tx frequency offset can be caused only by the differences in the actual reference frequency. to minimize these errors it is suggested to use the same crystal ty pe and the same pcb layout for the crystal placement on the rx and tx pcbs. to verify the possible rx-tx offset it is su ggested to measure the clk output of both chips with a high level of accuracy. do n ot measure the output at the xtl pin since the measurement process itself will change the reference frequency. since the carrier frequencies are derived from the reference frequency, having id entical reference frequencies and nominal frequency settings at the tx and rx side there should be no offset if the clk signals have identical frequencies. it is possible to monitor the actual rx-tx o ffset using the afc status report included in the status byte of the receiver. by r eading out the status byte from the receiver the actu al measured offset frequency will be report ed. in order to get accurate values the af c has to be disabled during the read by clearing th e "en" bit in the afc control command (bit 0). vdd l3 to rfp c1 50 ohm load l1 gnd to rfn c2 gnd c 1 , c 2 [pf] 3.9 l 1 [nh] 6.8 l 3 [nh] 100
SI4022 ? ? ? 0 c 0 0 c crystal selection guidelines the crystal oscillator of the SI4022 requires a 10 mhz parallel mode crystal. the circuit contains an integrated load capacitor in order to minimize the external component count. the internal load capacitance value is prog rammable from 8.5 pf to 16 pf in 0.5 pf st eps. with appropriate pcb layout, the total load capacitance value can be 10 pf to 20 pf so a variety of crystal types can be used. when the total load capacitance is not more than 20 pf and a wors t case 7 pf shunt capacitance (c ) value is expected for the c rystal, the oscillator is able to start up with any crystal having le ss than 300 ohms esr (equivalent se ries loss resistance). however, lower and esr values guarantee faster oscillator startup. it is recomme nded to keep the pcb parasitic capacitances on the xtl pin as low as possible. the crystal frequency is used as the reference of the pll, which generates the rf carrier frequency (f ). therefore f is directly proportional to the crystal frequency. the accuracy requirements for production tole rance, temperature drift and aging can thus be determined from the maximum allowable carrier frequency error. maximum xtal tolerances including temperature and aging [ppm] bit rate: bit rate: bit rate: bit rate: 2.4 kbps 9.6 kbps 38.4 kbps 115.2 kbps whenever a low frequency error is essential for the application, it is possible to ?pu ll? the crystal to the accurate frequency by changing the load capacitor value. the wide st pulling range can be achieved if the no minal required load capacitance of the cry stal is in the ?midrange?, for example 16 pf. the ?pull-ability? of the crystal is defined by its motional capacitance and c . n n no o ot t te e e:: there may be other requirements for the tx carrier accuracy with regards to the requirements as defined by standards and/or channel separations. c ? 20 40 60 transmitter deviation [+/- kh 80 100 z] 120 140 160 868 2 12 25 30 40 50 70 80 915 2 12 20 30 40 50 60 70 ? 20 40 60 transmitter deviation [+/- kh 80 100 z] 120 140 160 868 do not use 8 20 30 40 50 60 70 915 do not use 8 15 30 40 50 60 70 ? 20 40 60 transmitter deviation [+/- kh 80 100 z] 120 140 160 868 do not use do not use 10 20 30 40 50 70 915 do not use do not use 10 20 30 40 50 60 ? 20 40 transmitter deviation [+/- khz] 60 80 100 120 140 160 868 do not use do not use do not use do not use do not use 2 12 25 915 do not use do not use do not use do not use do not use 2 12 20
SI4022 ? ? ? 0 example applications: da ta packet transmission data packet structure an example data packet structure using thes i4022 ?SI4022 pair for data tran smission. this packet struct ure is an ex ample of how to use the high efficiency fifo mode at the receiver side: aa aa aa 2d d4 d 0 d 1 d 2 . . . d n synchron pattern the first 3 bytes compose a 24 bit length ?01? pattern to let enough time for the clock recovery of the receiver to lock. the n ext two bytes compose a 16 bit synchron pattern which is essential for the receiver?s fifo to find the byte synchron in the received bit stre am. the synchron patters is followed by the payload. the first byte transmitted after the synchron pattern (d in the picture above) wil l be the first received byte in the fifo. iii m m mp p po o or r rt t ta a an n nt t t::: the bytes of the data stream should follow each other continuously, otherwise the clock recovery circuit of the receiver s ide will be unable to track. further details of packet structures can be found in the ia ism-ugsb1 software development kit manual. preamble databytes (received in the fifo of the receiver)
SI4022 ? ? ? package information 16-pin tssop
SI4022 ? ? ? ordering information SI4022 universal ism band fsk transmitter description ordering number die see silicon labs demo boards and development kits description ordering number related resources description ordering number antenna development guide ia ism ? an2 note: volume orders must include chip revision to be accepted. ? ? ? ia4322 universal ism band fsk receiver see h ttp://www.silabs.com/integration for details antenna selection guide ia ism ? an1 ism chipset development kit ia ism ? dk3 SI4022 16-pin tssop SI4022-ic cc16 rev a0
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