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advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 1 sx8725 zoomingadc? for pressure and temperature sensing description the sx8725 is a data acquisition system based on semtechs low power zoomingadc? technology. it directly connects most types of miniature sensors with a general purpose microcontroller. with 1 differential input, it can adapt to multiple sensor systems. its digital outputs are used to bia s or reset the sensing elements. applications industrial pressure sensing industrial temperature sensing barometer compass features up to 16-bit differential data acquisition programmable gain: (1/12 to 1000) sensor offset compensation up to 15 times full scale of input signal 1 differential or 2 single-ended signal inputs programmable resolution versus speed versus supply current 2 digital outputs to bias sensors internal or external voltage reference internal time base low-power (250 ua for 16b @ 500 s/s) 2-wire interface ordering information device package reel quantity sx8725e083trt SX8725E083TDT mlpd-w-12 4x4 mlpd-w-12 4x4 3000 1000 1) available in tape and reel only 2) lead free, weee and rohs compliant. functional block diagram
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 2 sx8725 zoomingadc? for pressure and temperature sensing table of contents description........................................ ................................................... ................................................... ................1 applications....................................... ................................................... ................................................... ...............1 features ........................................... ................................................... ................................................... .................1 ordering information ............................... ................................................... ................................................... ........1 functional block diagram........................... ................................................... ................................................... ....1 absolute maximum ratings ........................... ................................................... ................................................... .4 electrical characteristics ......................... ................................................... ................................................... .......5 zoomingadc specifications.......................... ................................................... ................................................... .6 timing characteristics ............................. ................................................... ................................................... .......8 2-wire timing waveforms ............................ ................................................... ................................................... .8 pin configuration .................................. ................................................... ................................................... ...........9 marking information................................ ................................................... ................................................... .........9 pin description .................................... ................................................... ................................................... .............9 circuit description ................................ ................................................... ................................................... .........10 general description ................................ ................................................... ................................................... ........ 10 block diagram ...................................... ................................................... ................................................... ........... 10 vref ............................................... ................................................... ................................................... ................ 10 gpio ............................................... ................................................... ................................................... ................ 11 charge pump ........................................ ................................................... ................................................... .......... 12 rc oscillator ...................................... ................................................... ................................................... ............. 13 2-wire............................................. ................................................... ................................................... ............... 14 2-wire communication format ........................ ................................................... ................................................ 14 2-wire address..................................... ................................................... ................................................... ......... 14 zoomingadc ......................................... ................................................... ................................................... .........15 features ........................................... ................................................... ................................................... ............... 15 overview ........................................... ................................................... ................................................... .............. 15 zadc description................................... ................................................... ................................................... ......... 15 acquisition chain.................................. ................................................... ................................................... ........... 15 registers .......................................... ................................................... ................................................... ............... 17 zadc detailed functionality description ............ ................................................... ............................................... 18 continuous-time vs. on-request..................... ................................................... ................................................. 18 input multiplexers ................................. ................................................... ................................................... ........... 19 programmable gain amplifiers ....................... ................................................... ................................................... 20 pga & adc enabling................................. ................................................... ................................................... ..... 21 pga1 ............................................... ................................................... ................................................... ................ 21 pga2 ............................................... ................................................... ................................................... ................ 21 pga3 ............................................... ................................................... ................................................... ................ 21 adc characteristics ................................ ................................................... ................................................... ........ 22 conversion sequence ................................ ................................................... ................................................... ..... 22 over-sampling frequency ............................ ................................................... ................................................... .. 22 over-sampling ratio ................................ ................................................... ................................................... ....... 23 elementary conversions ............................. ................................................... ................................................... .... 23 resolution ......................................... ................................................... ................................................... .............. 24 conversion time and throughput..................... ................................................... ................................................. 25 output code format ................................. ................................................... ................................................... ...... 26 power saving modes ................................. ................................................... ................................................... ..... 27 registers map ...................................... ................................................... ................................................... ........... 28 registers descriptions ............................. ................................................... ................................................... ....... 28 rc register........................................ ................................................... ................................................... ............. 28 gpio registers ..................................... ................................................... ................................................... .......... 29 zadc registers ..................................... ................................................... ................................................... ......... 30 mode register ...................................... ................................................... ................................................... ........... 31 optional operating modes: external voltage referenc e option ........................................... ............................... 32 application hints.................................. ................................................... ................................................... ..........33 recommended operation mode and registers settings.. ................................................... ................................. 33 operation mode..................................... ................................................... ................................................... .......... 33
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 3 sx8725 zoomingadc? for pressure and temperature sensing registers settings ................................. ................................................... ................................................... .......... 33 schematic.......................................... ................................................... ................................................... .............. 34 input impedance.................................... ................................................... ................................................... .......... 35 switched capacitor principle ....................... ................................................... ................................................... ... 36 pga settling or input channel modifications ........ ................................................... ............................................. 37 pga gain & offset, linearity and noise ............. ................................................... ............................................... 37 frequency response ................................. ................................................... ................................................... ..... 38 power reduction .................................... ................................................... ................................................... ......... 39 recommended design for other 2-wire devices connect ion ................................................ ........................... 39 typical performance ................................ ................................................... ................................................... ......40 linearity .......................................... ................................................... ................................................... ................. 40 integral non-linearity............................. ................................................... ................................................... ......... 40 differential non-linearity......................... ................................................... ................................................... ........ 43 noise .............................................. ................................................... ................................................... ................. 44 gain error and offset error ........................ ................................................... ................................................... ..... 46 power consumption .................................. ................................................... ................................................... ...... 47 pcb layout considerations.......................... ................................................... ................................................... 49 how to evaluate.................................... ................................................... ................................................... ..........49 package outline drawing: mlpd-w-12 4x4............. ................................................... .......................................50 land pattern drawing: mlpd-w-12 4x4................ ................................................... ..........................................51 tape and reel specification ........................ ................................................... ................................................... .52
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 4 sx8725 zoomingadc? for pressure and temperature sensing absolute maximum ratings exceeding the specifications below may result in pe rmanent damage to the device or device malfunction. operation outside the parameters specified in the e lectrical characteristics section is not implied. parameter symbol comments / conditions min max unit power supply v batt v ss - 0.3 5.7 v storage temperature t store -55 150 c temperature under bias t bias -40 140 c v vr_p max sensor common mode v vr_n v ss - 300 v batt + 300 mv input voltage v ss - 300 v batt + 300 mv peak reflow temperature t pkg 260 c notes: this device is esd sensitive. use of standard esd h andling precautions is required.
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 5 sx8725 zoomingadc? for pressure and temperature sensing electrical characteristics all values are valid within the operating condition s unless otherwise specified. parameter symbol comments / conditions min typ max u nit operating conditions power supply v batt 2.4 5.5 v operating temperature t op -40 125 c current consumption 16 b @ 250 sample/s adc, f s = 125 khz 250 300 16 b @ 1 ksample/s pga3 + adc, f s = 500 khz 700 800 active current, @ 30 c, 5.5 v i op 16 b + gain 1000 @ 1 ksample/s pga3,2,1 + adc, f s = 500khz 1000 1200 a 16 b @ 250 sample/s pga3 + adc, f s = 125 khz 150 16 b @ 1 ksample/s pga3 + adc, f s = 500 khz 300 active current, @ 30 c, 3.3 v i op 16 b + gain 1000 @ 1 ksample/s pga3,2,1 + adc, f s = 500khz 850 a @ 30 c 75 200 up to 85 c 100 sleep current i sleep @125 c 150 na time base max adc over-sampling frequency f smax @ 25 c 450 500 550 khz min adc over-sampling frequency f smin @ 25 c 56.25 62.5 68.75 khz digital i/o input logic high v ih 0.7 v batt input logic low v il 0.3 v batt output logic high v oh i oh < 4ma v batt -0.4 v output logic low v ol i ol < 4ma 0.4 v vref: internal bandgap reference absolute output voltage v batt > 3v 1.19 1.22 1.25 v variation over temperature v batt > 3v, ref to 25 c -1 +1 % total output noise v batt > 3v, rms, broadband 1 mv
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 6 sx8725 zoomingadc? for pressure and temperature sensing zoomingadc specifications unless otherwise specified: temperature t a = +25 c, v dd = +5v, gnd = 0v, v ref, adc = +5v, v in = 0v, over-sampling frequency f s = 250 khz, pga3 on with gain = 1, pga1&pga2 off , offsets gdoff 2 = gdoff 3 = 0. power operation: normal (ib_amp_adc[1:0] = ib_amp_pga[1:0] = '01'). for resolution n = 12 bits: osr = 32 and n elconv = 4. for resolution n = 16 bits: osr = 512 and n elconv = 2. bandgap chopped at n elconv rate. parameter symbol comments / conditions min typ max u nit analog input gain = 1, osr = 32 (note 1) -2.42 2.42 v gain = 100, osr = 32 -24.2 24.2 mv differential input voltage ranges v in = (v inp - v inn ) gain = 1000, osr = 32 -2.42 2.42 mv reference voltage range v ref, adc = (v refp C v refn ) v dd v programmable gain amplifier (pga) total pga gain gd tot (note 1) 1/12 1000 v/v pga1 gain gd 1 see table 5 1 10 v/v pga2 gain gd 2 see table 6 1 10 v/v pga3 gain gd 3 step = 1/12 v/v, see table 8 0 127/12 v/v gain setting precision (each stage) -3 0.5 3 % gain temperature dependence 5 ppm/c pga2 offset gdoff 2 step = 0.2 v/v, see table 7 -1 1 v/v pga3 offset gdoff 3 step = 1/12 v/v, see table 9 -63/12 63/12 v/v offset setting precision (pga2 or 3) (note 2) -3 0.5 3 % offset temperature dependence 5 ppm/c gain = 1 (note 3) 1500 k input impedance pga1 gain = 10 (note 3) 150 k input impedance pga2, pga3 maximal gain (note 3) 1 50 k pga1 (note 4) 205 v pga2 (note 5) 340 v output rms noise pga3 (note 6) 365 v adc static performance resolution, n (note 7) 6 16 bits no missing codes (note 8) 16 bits gain error (note 9) 0.15 % 1 % offset error n = 16 bits (note 10) 1 lsb n = 12 bits (note 11) 0.6 lsb integral non-linearity, inl n = 16 bits (note 11) 1.5 lsb n = 12 bits (note 12) 0.5 lsb differential non-linearity, dnl n = 16 bits (note 12) 0.5 lsb common mode input range v ss -0.3 v batt +0.3 v vdd = 5v 0.3v (note 13) 78 db power supply rejection ratio psrr vdd = 3v 0.3v (note 13) 72 db adc dynamic performance n = 12 bits (note 14) 133 cycles/f s conversion time t conv n = 16 bits (note 14) 1027 cycles/f s n = 12 bits, f s = 250khz 1.88 ksps throughput rate (continuous mode) 1/t conv n = 16 bits, f s = 250khz 0.485 ksps nbr of initialization cycles n init 0 2 cycles
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 7 sx8725 zoomingadc? for pressure and temperature sensing parameter symbol comments / conditions min typ max u nit nbr of end conversion cycles n end 0 5 cycles pga stabilization delay (note 15) osr cycles adc digital output output data coding binary twos complement see table 15 and table 16 power supply voltage supply range v dd 2.4 5 5.5 v analog quiescent current only zoomingadc total consumption i q v dd = 5v/3v 800/675 a adc only consumption v dd = 5v/3v 260/190 a pga1 consumption v dd = 5v/3v 190/170 a pga2 consumption v dd = 5v/3v 150/135 a pga3 consumption v dd = 5v/3v 200/180 a analog power dissipation all pgas & adc active normal power mode v dd = 5v/3v (note 16) 4.0/2.0 mw 3/4 power reduction mode v dd = 5v/3v (note 17) 3.2/1.6 mw 1/2 power reduction mode v dd = 5v/3v (note 18) 2.4/1.1 mw 1/4 power reduction mode v dd = 5v/3v (note 19) 1.5/0.7 mw temperature operating range -40 125 c notes: (1) gain defined as overall pga gain gd tot = gd 1 gd 2 gd 3 . maximum input voltage is given by: v in, max = (v ref,adc /2) (osr/osr+1). (2) offset due to tolerance on gdoff 2 or gdoff 3 setting. for small intrinsic offset, use only adc and pga1. (3) measured with block connected to inputs through amux block. normalized input sampling frequency fo r input impedance is f s = 500khz. this figure must be multiplied by 2 for f s = 250khz, 4 for f s = 125khz. input impedance is proportional to 1/ f s . (4) figure independent on pga1 gain and sampling fr equency f s . (5) figure independent on pga2 gain and sampling fr equency f s . (6) figure independent on pga3 gain and sampling fr equency f s . (7) resolution is given by n = 2 log2( osr ) + log2( n elconv ). osr can be set between 8 and 1024, in powers of 2. n elconv can be set to 1, 2, 4 or 8. (8) if a ramp signal is applied to the input, all d igital codes appear in the resulting adc output dat a. (9) gain error is defined as the amount of deviatio n between the ideal (theoretical) transfer function and the measured transfer function (with the offset error removed). (10) offset error is defined as the output code err or for a zero volt input (ideally, output code = 0) . for 1 lsb offset, n elconv must be 3 2. (11) inl defined as the deviation of the dc transfe r curve of each individual code from the best-fit s traight line. this specification holds over the full scale. (for 16 bits inl set pga3 on). (12) dnl is defined as the difference (in lsb) betw een the ideal (1 lsb) and measured code transitions for successive codes. (13) figures for gains = 1 to 100. psrr is defined as the amount of change in the adc output value as the power supply voltage changes. (14) conversion time is given by: t conv = ( n elconv (osr + 1) + 1) / f s . osr can be set between 8 and 1024, in powers of 2. n elconv can be set to 1, 2, 4 or 8. (15) pgas are reset after each writing operation to registers regaccfg1-5 . the adc must be started after a pga or inputs com mon- mode stabilization delay. this is done by writing b it start several cycles after pga settings modifica tion or channel switching. delay between pga start or input channel switching and ad c start should be equivalent to osr (between 8 and 1024) number of cycles. this delay does not apply to conversions made witho ut the pgas. (16) nominal (maximum) bias currents in pgas and ad c, i.e. ib_amp_pga[1:0] = '11' and ib_amp_adc[1:0] = '11'. (17) bias currents in pgas and adc set to 3/4 of no minal values, i.e. ib_amp_pga[1:0] = '10', ib_amp_a dc[1:0] = '10'. (18) bias currents in pgas and adc set to 1/2 of no minal values, i.e. ib_amp_pga[1:0] = '01', ib_amp_a dc[1:0] = '01'. (19) bias currents in pgas and adc set to 1/4 of no minal values, i.e. ib_amp_pga[1:0] = '00', ib_amp_a dc[1:0] = '00'.
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 8 sx8725 zoomingadc? for pressure and temperature sensing timing characteristics parameter symbol comments / conditions min typ max u nit interrupt (ready) timing specification ready pulse width (2) t irq 1 1/f s 2-wire timing specifications(1) scl clock frequency f scl 0 400 khz scl low period t low 1.3 s scl high period t high 0.6 s 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 s start condition hold time t hd;sta 0.6 s stop condition hold time t su;sto 0.6 s bus free time between stop and start t buf 1.3 s input glitch suppression t sp 50 ns notes: (1) all timing specifications are referred to vilmi n and vihmax voltage levels defined for the scl and sda pins. (2) the ready pulse indicates end of conversion. th is is a low going pulse of duration equal to one cy cle of the adc sampling rate. 2-wire timing waveforms figure 1 - 2-wire start and stop timings figure 2 - 2-wire data timings sda scl t su;sta t hd;sta t su;sto t buf sda scl t low t high t hd;dat t su;dat t sp
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 9 sx8725 zoomingadc? for pressure and temperature sensing pin configuration marking information pin description pin name type function 1 nc - not connected 2 nc - not connected 3 v batt power input 2.4v to 5.5v power supply 4 v ss power input chip ground 5 ready digital output conversion complete flag. digital output sensor drive (v batt or v ss ) 6 d 1 digital io + analog v ref input in optional operating mode digital output sensor drive (v batt or v ss ) 7 d 0 digital io + analog v ref output in optional operating mode 8 sda digital io 2-wire data 9 scl digital io 2-wire clock. up to 400khz. 10 v pump power io charge pump output. raises adc supply above v batt if v batt supply is too low. recommended range for capacitor is 1nf to 10 nf. co nnect the capacitor to gnd. 11 ac 2 analog input differential sensor input in conjunct ion with ac 3 12 ac 3 analog input differential sensor input in conjunct ion with ac 2 13 v ss power input bottom ground pad (1) notes: (1) this pin is internally connected to v ss . it should also be connected to v ss on pcb to reduce noise and improve thermal behavio r. 8725 yyww xxxxx xxxxx yyww = date code xxxx = semtech lot number
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 10 sx8725 zoomingadc? for pressure and temperature sensing circuit description general description the sx8725 is a complete low-power acquisition path with programmable gain, acquisition speed and resolution. block diagram figure 3 - sx8725 block diagram vref the internally generated v ref is a trimmed bandgap reference with a nominal valu e of 1.22v that provides a stable voltage reference for the zoomingadc. this reference voltage is directly connected to one of the zoomingadc reference multiplexer inputs. the bandgap voltage stability is only guaranteed fo r v batt voltages of 3v and above. as v batt drops down to 2.4v, the bandgap voltage could reduce by up to 50m v. the bandgap has relatively weak output drive so it is recommended that if the bandgap is required as a signal input then pga1 must be enabled with gain = 1. ac0 signal mux + - + - ref mux ready ac3 ac2 ac1 pga adc v ref + - zoomingadc tm v pump v batt scl sda d1/ref in d0/ref out sx8725 vss control logic gpio charge pump 4mhz osc i 2 c
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 11 sx8725 zoomingadc? for pressure and temperature sensing gpio the gpio block is a multipurpose 4 bit input/output port. in addition to digital behavior, d0 and d1 p ins can be programmed as analog pins in order to be used as ou tput (reference voltage monitoring) and input for a n external reference voltage (for further details see figure 14, figure 15, figure 16 and figure 17) . each port terminal can be individually selected as digital in put or output. figure 4 - gpio block diagram the direction of each bit within the gpio block (in put only or input/output) can be individually set u sing the 4 th and 5 th bits of the regout register. if d[x]_dir = 1, both the input and outp ut buffer are active on the corresponding gpio block pin. if d[x]_dir = 0, the corresponding gpio block pin is an input only and t he output buffer is in high impedance. after power on reset the gpio block pins are in input/output mode (d[x]_dir are reset to 1) the input values of gpio block are available in regin register (read only). reading is always direct C t here is no debounce function in the gpio block. in case of possible noise on input signals, an external hardwa re filter has to be realized. the input buffer is also active when the gpio block is defined as output and the e ffective value on the pin can be read back. data stored in the 1 st and 2 nd bits of regout register are outputted at gpio block if d[x]_dir = 1. the default values after power on reset is low (0). the digital pins are able to deliver a driving curr ent up to 8 ma. when the bits vref_d0_out and vref_d1_in in the regmode register are set to 1 the d0 and d1 pins digital behavior are automatically bypassed in orde r to either input or output the voltage reference s ignals. regout[4] regout[5] regout[0] regin[0] regout[1] regin[1] v ref + - d1/ref in d0/ref out regmode[0] 01 regmode[1] 01 0 1 zoomingadc
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 12 sx8725 zoomingadc? for pressure and temperature sensing charge pump this block generates a supply voltage able to power the analog switch drive levels on the chip. the minimum acceptable switch supply is 3v which me ans that if v batt drops below 3v then the block should be activated to generate a voltage of 3v or above. if v batt is greater than 3v then v batt may be switched straight through to the v pump output. if control input bit mult_force_off = 1 in regmode register then the charge pump is disabled and v batt is permanently connected to v pump . if control input bit mult_force_on = 1 in regmode register then the charge pump is permanently enabl ed. this overrides mult_force_off bit in regmode register. if mult_force_on = 0 and mult_force_off = 0 bits in regmode register then the charge pump will start if v batt drops below 3v, otherwise v batt will be switched directly through to v pump . these controls are supplied to give the user the op tion of fixing the charge pump state to avoid it tu rning off and on when v batt is close to 3v. the cell will use the on-chip bandgap reference and comparator to detect when v batt is too low. when activated, the block will use the charge pump to bo ost the v batt voltage to above 3v but with diode limiting to ensure that the generated voltage never exceeds 0.7 v above v batt . an external capacitor is required on v pump whenever the power supply is supposed to be less or drop below 3v. this capacitor should be large enough to ensure tha t generated voltage is smooth enough to avoid affec ting conversion accuracy but not so large that it gives an unacceptable settling time. a recommended value is around 2.2nf. the block will also indicate when the pumped output voltage is sufficiently high to allow adc conversi ons to be started. this will be a simple comparison which wil l give a ready signal when the v pump output is 3v or above.
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 13 sx8725 zoomingadc? for pressure and temperature sensing rc oscillator this block provides the master clock reference for the chip. it produces a clock at 4 mhz which is div ided internally in order to generate the clock sources n eeded by the other blocks. the oscillator technique is a low power relaxation design and it is designed to vary as little as poss ible over temperature and supply voltage. this oscillator is trimmed at manufacture chip test . the rc oscillator will start up after a chip reset to allow the trimming values to be read and calibra tion registers and 2-wire address set to their programmed values. once this has been done, the oscillator will be shu t down and the chip will enter a sleep state while waiting for an 2-wire communication.
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 14 sx8725 zoomingadc? for pressure and temperature sensing 2-wire the 2-wire interface gives access to the chip regis ters. it complies with the 2-wire protocol specific ations, restricted to the slave side of the communication. general features: slave only operation fast mode operation (up to 400 khz) combined read and write mode support general call reset support 7-bit device address customization stretch 2-wire clock scl only before sending ack/n ack the interface handles 2-wire communication at the t ransaction level: the processor is only aware of re ad and writes transactions. a read transaction is an exter nal request to get the content of system memory loc ation and a write transaction is an external request to write the content of a system memory location. 2-wire communication format figure 5 - timing diagram for reading from sx8725 figure 6 - timing diagram for writing to the sx8725 figure 7 - timing diagram for reading an adc sample from sx8725 2-wire address the default 2-wire slave address is 1001000 in bina ry. this is the standard part 2-wire slave address. oth er addresses between 1001001 and 1001111 are availa ble by special request. start slave address ack w memory address ack start slave address ack r data nack stop master master master master sx8725 sx8725 sx8725 1 0 0 1 0 0 0 0 0 1 9 1 9 1 9 1 9 a7 a6 a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 1 0 0 1 0 0 0 1 sda scl start slave address ack w memory address ack start slave address ack w data ack stop master sx8725 master master master sx8725 sx8725 master sx8725 1 9 1 9 1 9 1 9 1 0 0 1 0 0 0 0 0 a7 a6 a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 1 0 0 1 0 0 0 0 sda scl start slave address ack w regacoutmsb ack start slave address ack r data nack stop master master master master sx8725 sx8725 sx8725 1 0 0 1 0 0 0 0 0 1 9 1 9 1 9 1 9 0 d7 d6 d5 d4 d3 d2 d1 d0 1 0 0 1 0 0 0 1 sda scl ready 1 1 0 0 0 0 1 start slave address ack w regacoutlsb ack start slave address ack r data nack stop master master master master sx8725 sx8725 sx8725 1 0 0 1 0 0 0 0 0 1 9 1 9 1 9 1 9 0 d7 d6 d5 d4 d3 d2 d1 d0 1 0 0 1 0 0 0 1 sda scl ready 1 1 0 0 0 0 0 ... ... ... ...
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 15 sx8725 zoomingadc? for pressure and temperature sensing zoomingadc features the zoomingadc is a complete and versatile low-power analog front-end interface typically intended for s ensing applications. in the following text the zoomingadc will be referred a s zadc. the key features of the zadc are: programmable 6 to 16-bit dynamic range over-sample d adc flexible gain programming between 0.5 and 1000 flexible and large range offset compensation 2-channel differential or 3-channel single-ended i nput 2-channel differential reference inputs power saving modes overview figure 8 - zadc general functional block diagram the total acquisition chain consists of an input mu ltiplexer, 3 programmable gain amplifier stages and an over sampled a/d converter. the reference voltage can be selected on two different channels. two offset compen sation amplifiers allow for a wide offset compensation range . the programmable gain and offset allow the applica tion to zoom in on a small portion of the reference voltage defined input range. zadc description acquisition chain figure 8 shows the general block diagram of the acquisition chain (ac). a control block (not shown in figure 8) manages all communications with the 2-wire peripher al. the clocking is derived from the internal 4 mhz oscillator. analog inputs can be selected through a 4 input mul tiplexer, while reference input is selected between t wo differential channels. it should however be noted that only 3 acq uisition channels (including the v ref ) are available when configured as single ended since the input amplifie r is always operating in differential mode with both positive and negative input selected through the multiplexer. the core of the zooming section is made of three di fferential programmable amplifiers (pga). after sel ection of an input and reference signals v in and v ref,adc combination, the input voltage is modulated and am plified through input selection analog inputs reference selection reference inputs gd1 off2 gd2 off3 gd3 + - + - adc f s f s v in v d1 v d2 v in,adc v ref,adc pga1 pga2 pga3 gain 1 gain 2 offset 2 gain 3 offset 3 v ss v ref ac 2 ac 3 v ss v batt v ss v ref ac 0 ac 1 - +- + zoom 16
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 16 sx8725 zoomingadc? for pressure and temperature sensing stages 1 to 3. fine gain programming up to 1'000 v/ v is possible. in addition, the last two stages prov ide programmable offset. each amplifier can be bypassed if needed. the output of the pga stages is directly fed to the analog-to-digital converter (adc), which converts the signal v in,adc into digital. like most adcs intended for instrumentation or sens ing applications, the zoomingadc is an over-sampled converter (see note 1 ). the adc is a so-called incremental converter; wi th bipolar operation (the adc accepts both positive and negative differential input volta ges). in first approximation, the adc output result relative to full-scale ( fs ) delivers the quantity: 2/ 2/ , , adc ref adc in s adc v v f out @ equation 1 in two's complement (see equation 4 and equation 5 for details). the output code out adc is -fs/2 to + fs/2 for v in,adc @ -v ref,adc /2 to +v ref,adc /2 respectively. as will be shown, v in,adc is related to input voltage v in by the relationship: adc ref tot in tot adc in v gdoff v gd v , , - = (v) equation 2 where gd tot is the total pga gain, and gdoff tot is the total pga offset. 1 note: over-sampled converters are operated with a s ampling frequency f s much higher than the input signal's nyquist rate ( typically f s is 20-1'000 times the input signal bandwidth). the sam pling frequency to throughput ratio is large (typic ally 10-500). these converters include digital decimation filtering. they are mainly used for high resolution, and/or low-to-medium speed app lications.
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 17 sx8725 zoomingadc? for pressure and temperature sensing registers the system has a bank of eight 8-bit registers: six registers are used to configure the acquisition ch ain ( regaccfg0 to 5 ), and two registers are used to store the output c ode of the analog-to-digital conversion ( regacoutmsb & lsb ). bit position register name 7 6 5 4 3 2 1 0 regacoutlsb out[7:0] regacoutmsb out[15:8] regaccfg0 default values: start 0 set_nelc[1:0] 01 set_osr[2:0] 010 cont 0 - 0 regaccfg1 default values: ib_amp_adc[1:0] 11 ib_amp_pga[1:0] 11 enable[3:0] 0000 regaccfg2 default values: fin[1:0] 00 pga2_gain[1:0] 00 pga2_offset[3:0] 0000 regaccfg3 default values: pga1_g 0 pga3_gain[6:0] 0001100 regaccfg4 default values: - 0 pga3_offset[6:0] 0000000 regaccfg5 default values: busy 0 def 0 amux[4:0] 00000 vmux 0 table 1 - peripheral registers to configure the acq uisition chain (ac) and to store the analog-to-digital conversion (adc) result with: out: (r) digital output code of the analog-to-digi tal converter. (msb = out[15]) start: (w) setting this bit triggers a single conv ersion (after the current one is finished). this bi t always reads back 0. set_nelc: (rw) sets the number of elementary conve rsions to 2 set_nelc[1:0]. to compensate for offset s, the input signal is chopped between elementary conversions (1,2,4,8). set_osr: (rw) sets the over-sampling rate (osr) of an elementary conversion to 2(3+set_osr[2:0]). osr = 8, 16, 32, ..., 512, 1024. cont: (rw) setting this bit starts a conversion. a new conversion will automatically begin as long as the bit remains at 1. test: bit only used for test purposes. in normal m ode, this bit is forced to 0 and cannot be overwrit ten. ib_amp_adc: (rw) sets the bias current in the adc to 0.25*(1+ ib_amp_adc[1:0]) of the normal operatio n current (25, 50, 75 or 100% of nominal current). to be used for low-power, low-speed operation. ib_amp_pga: (rw) sets the bias current in the pgas to 0.25*(1+ib_amp_pga[1:0]) of the normal operatio n current (25, 50, 75 or 100% of nominal current). to be used for low-power, low-speed operation. enable: (rw) enables the adc modulator (bit 0) and the different stages of the pgas (pgai by bit i=1, 2,3). pga stages that are disabled are bypassed. fin: (rw) these bits set the over sampling frequen cy of the acquisition chain. expressed as a fractio n of the oscillator frequency, the sampling frequency is given as: 11 500 khz, 10 250 khz, 01 125 khz, 00 62.5 khz. pga1_gain: (rw) sets the gain of the first stage: 0 1, 1 10. pga2_gain: (rw) sets the gain of the second stage: 00 1, 01 2, 10 5, 11 10. pga3_gain: (rw) sets the gain of the third stage t o pga3_gain[6:0] 1/12. pga2_offset: (rw) sets the offset of the second st age between C1 and +1, with increments of 0.2. the msb gives the sign (0 ? positive, 1 ? negative); amplitude is coded with the bits pga2_o ffset[5:0]. pga3_offset: (rw) sets the offset of the third sta ge between C5.25 and +5.25, with increments of 1/12 . the msb gives the sign (0 ? positive, 1 ? negative); amplitude is coded with the bits pga3_o ffset[5:0]. busy: (r) set to 1 if a conversion is running. def: (w) sets all values to their defaults (pga di sabled, max speed, nominal modulator bias current, 2 elementary conversions, over-sampling rate of 32) and starts a new conversi on without waiting the end of the preceding one. amux(4:0): (rw) amux(4) sets the mode (0 differential inputs, 1 single ended inputs with a 0 = common reference) amux(3) sets the sign (0 straight, 1 cross) amux(2:0) sets the channel. vmux: (rw) sets the differential reference channel (0 v batt , 1 v ref ). (r = read; w = write; rw = read & write)
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 18 sx8725 zoomingadc? for pressure and temperature sensing zadc detailed functionality description continuous-time vs. on-request the adc can be operated in two distinct modes: "con tinuous-time" and "on-request" modes (selected usin g the bit cont). in "continuous-time" mode, the input signal is repe atedly converted into digital. after a conversion i s finished, a new one is automatically initiated. the new value i s then written in the result register, and the corr esponding internal trigger pulse is generated. this operation is sketched in figure 9. the conversion time in t his case is defined as t conv . figure 9 - adc "continuous-time" operation in the "on-request" mode, the internal behavior of the converter is the same as in the "continuous-tim e" mode, but the conversion is initiated on user request (wi th the start bit). as shown in figure 10, the conv ersion time is also t conv . figure 10 - adc "on-request" operation t conv irq/ready busy output code regacout[15:0] internal trig
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 19 sx8725 zoomingadc? for pressure and temperature sensing input multiplexers the zoomingadc has eight analog inputs ac 0 to ac 7 and four reference inputs ac_r 0 to ac_r 3 . let us first define the differential input voltage v in and reference voltage v ref,adc respectively as: inn inp in v v v - = (v) equation 3 and: refn refp adc ref v v v - = , (v) equation 4 as shown in table 2, the inputs can be configured i n two ways: either as 4 differential channels (v in1 = ac 1 - ac 0 ,..., v in3 = ac 5 C ac 4 ), or ac 0 can be used as a common reference, providing 5 sig nal paths all referred to ac 0 . the control word for the analog input selection i s amux[4:0]. notice that the bit amux[3] controls t he sign of the input voltage. amux[4:0] (regaccfg5[5:1]) v inp v inn amux[4:0] (regaccfg5[5:1]) v inp v inn 00x00 ac 1 (v ref ) ac 0 (v ss ) 01x00 ac 0 (v ss ) ac 1 (v ref ) 00x01 ac 3 ac 2 01x01 ac 2 ac 3 10000 ac 0 (v ss ) 11000 ac 0 (v ss ) 10001 ac 1 (v ref ) 11001 ac 1 (v ref ) 10010 ac 2 11010 ac 2 10011 ac 3 ac 0 (v ss ) 11011 ac 0 (v ss ) ac 3 table 2 - analog input selection similarly, the reference voltage is chosen among tw o differential channels ( v ref,adc = ac_r 1 - ac_r 0 or v ref,adc = ac_r 3 - ac_r 2 ) as shown in table 3. the selection bit is vmux. t he reference inputs v refp and v refn (common-mode) can be up to the power supply range. vmux (regaccfg5[0]) v refp v refn 0 ac_r 1 (v batt ) ac_r 0 (v ss ) 1 ac_r 3 (v ref ) ac_r 2 (v ss ) table 3 - analog reference input selection
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 20 sx8725 zoomingadc? for pressure and temperature sensing programmable gain amplifiers as seen in figure 8, the zooming function is implem ented with three programmable gain amplifiers (pga) . these are: pga1: coarse gain tuning pga2: medium gain and offset tuning pga3: fine gain and offset tuning. should be set o n for high linearity data acquisition all gain and offset settings are realized with rati os of capacitors. the user has control over each pg a activation and gain, as well as the offset of stages 2 and 3. these functions are examined hereafter. enable[3:0] (regaccfg1[3:0]) block xxx0 adc disabled xxx1 adc enabled xx0x pga1 disabled xx1x pga1 enabled x0xx pga2 disabled x1xx pga2 enabled 0xxx pga3 disabled 1xxx pga3 enabled table 4 - adc & pga enabling pga1_gain (regaccfg3[7]) pga1 gain gd 1 (v/v) 0 1 1 10 table 5 - pga1 gain settings pga2_gain[1:0] (regaccfg2[5:4]) pga2 gain gd 2 (v/v) 00 1 01 2 10 5 11 10 table 6 - pga2 gain settings pga2_offset[3:0] (regaccfg2[3:0]) pga2 offset gdoff 2 (v/v) 0000 0 0001 +0.2 0010 +0.4 0011 +0.6 0100 +0.8 0101 +1 1001 -0.2 1010 -0.4 1011 -0.6 1100 -0.8 1101 -1 table 7 - pga2 offset settings pga3_gain[6:0] (regaccfg3[6:0]) pga3 gain gd 3 (v/v) 0000000 0 0000001 1/12(=0.083) ... ... 0000110 6/12 ... ... 0001100 12/12 0010000 16/12 ... 0100000 32/12 ... 1000000 64/12 ... 1111111 127/12(=10.58) table 8 - pga3 gain settings pga3_offset[6:0] (regaccfg4[6:0]) pga3 offset gdoff 3 (v/v) 0000000 0 0000001 +1/12(=+0.083) 0000010 +2/12 ... ... 0010000 +16/12 ... ... 0100000 +32/12 ... ... 0111111 +63/12(=+5.25) 1000000 0 1000001 -1/12(=-0.083) 1000010 -2/12 ... ... 1010000 -16/12 ... ... 1100000 -32/12 ... ... 1111111 -63/12(=-5.25) table 9 - pga3 offset settings
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 21 sx8725 zoomingadc? for pressure and temperature sensing pga & adc enabling depending on the application objectives, the user m ay enable or bypass each pga stage. this is done according to the word enable and the coding given i n table 4. to reduce power dissipation, the adc can also be inactivated while idle. pga1 the first stage can have a buffer function (unity g ain) or provide a gain of 10 (see table 5). the vol tage v d1 at the output of pga1 is: in d v gd v = 1 1 (v) equation 5 where gd 1 is the gain of pga1 (in v/v) controlled with the b it pga1_gain. pga2 the second pga has a finer gain and offset tuning c apability, as shown in table 6 and table 7. the vol tage v d2 at the output of pga2 is given by: adc ref d d v gdoff v gd v , 2 1 2 2 - = (v) equation 6 where gd 2 and gdoff 2 are respectively the gain and offset of pga2 (in v /v). these are controlled with the words pga2_gain[1:0] and pga2_offset[3:0]. pga3 the finest gain and offset tuning is performed with the third and last pga stage, according to the cod ing of table 8 and table 9. the output of pga3 is also the input of the adc. thus, similarly to pga2, we find that the voltage entering the adc is given by: adc ref d adc in v gdoff v gd v , 3 2 3 , - = (v) equation 7 where gd 3 and gdoff 3 are respectively the gain and offset of pga3 (in v /v). the control words are pga3_gain[6:0] and pga3_offset[6:0]. to remain with in the signal compliance of the pga stages, the condition: dd d d v v v < 2 1 , (v) equation 8 must be verified. finally, combining equations 5 to 7 for the three p ga stages, the input voltage v in,adc of the adc is related to v in by: adc ref tot in tot adc in v gdoff v gd v , , - = (v) equation 9 where the total pga gain is defined as: 1 2 3 gd gd gd gd tot = (v/v) equation 10 and the total pga offset is: 2 3 3 gdoff gd gdoff gdoff tot + = (v/v) equation 11
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 22 sx8725 zoomingadc? for pressure and temperature sensing adc characteristics the main performance characteristics of the adc (re solution, conversion time, etc.) are determined by three programmable parameters. the setting of these param eters and the resulting performances are described later. over-sampling frequency f s over-sampling ratio osr number of elementary conversions nelconv conversion sequence a conversion is started each time the bit start or the bit def is set. as depicted in figure 11, a com plete analog-to-digital conversion sequence is made of a set of n elconv elementary incremental conversions and a final quantization step. each elementary conversion is made of (osr+1) over-sampling periods t s =1/f s , i.e.: ( ) fs osr t elconv 1 + = (s) equation 12 the result is the mean of the elementary conversion results. an important feature is that the elementa ry conversions are alternatively performed with the of fset of the internal amplifiers contributing in one direction and the other to the output code. thus, converter inter nal offset is eliminated if at least two elementary sequences are performed (i.e. if n elconv 3 2). a few additional clock cycles are also require d to initiate and end the conversion properly. figure 11 - analog-to-digital conversion sequence note : the internal bandgap reference state may be forced high or low, or may be set to toggle during convers ion at either the same rate or half the rate of the elementary conversion. this may be useful to help eliminate bandgap related internal o ffset voltage and 1/f s noise. over-sampling frequency the word fin[1:0] (see table 10) is used to select the over-sampling frequency f s . the over-sampling frequency is derived from the 4mhz oscillator clock. fin[1:0] (regaccfg2[7:6]) over-sampling frequency f s (hz) 00 62.5 khz 01 125 khz 10 250 khz 11 500 khz table 10 - over-sampling frequency settings init elementary conversion elementary conversion elementary conversion elementary conversion end conversion index offset 1 2 n elconv -1 n elconv conversion result + - + - t conv
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 23 sx8725 zoomingadc? for pressure and temperature sensing over-sampling ratio the over-sampling ratio ( osr ) defines the number of integration cycles per elem entary conversion. its value is set with the word set_osr[2:0] in power of 2 steps (see table 11) given by: [ ] 0:2 _ 3 2 osr set osr + = equation 13 set_osr[2:0] (regaccfg0[4:2]) over-sampling ratio osr (-) 000 8 001 16 010 32 011 64 100 128 101 256 110 512 111 1024 table 11 - over-sampling ratio settings elementary conversions as mentioned previously, the whole conversion seque nce is made of a set of n elconv elementary incremental conversions. this number is set with the word set_n elc[1:0] in power of 2 steps (see table 12) given b y: [ ] 0:1 _ 2 nelc set elconv n = equation 14 set_nelc[1:0] (regaccfg0[6:5]) # of elementary conversions n elconv (-) 00 1 01 2 10 4 11 8 table 12 - number of elementary conversion settings as already mentioned, n elconv must be equal or greater than 2 to reduce internal amplifier offsets.
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 24 sx8725 zoomingadc? for pressure and temperature sensing resolution the theoretical resolution of the adc, without cons idering thermal noise, is given by: ( ) ( ) elconv n osr n 2 2 log log 2 + = (bits) equation 15 figure 12 - resolution vs. set_osr[2:0] and set_nel c[1:0] using look-up table 13 or the graph plotted in figu re 12, resolution can be set between 6 and 16 bits. notice that, because of 16-bit register use for the adc ou tput, practically the resolution is limited to 16 bits , i.e. n 16. even though the resolution is truncated to 16 bit by the output register size, it may make sense to set osr and n elconv to higher values in order to reduce the influence of the thermal noise in the pga and of external noises (see section pga gain & offset, li nearity and noise in page 37). set_nelc[1:0] set_osr [2:0] 00 01 10 11 000 6 7 8 9 001 8 9 10 11 010 10 11 12 13 011 12 13 14 15 100 14 15 16 16 101 16 16 16 16 110 16 16 16 16 111 16 16 16 16 note : shaded area: resolution truncated to 16 bits due to output register size regacout [15:0] table 13 - resolution vs. set_osr[2:0] and set_nelc [1:0] settings 5 7 9 11 13 15 17 000 001 010 011 100 101 110 111 set_osr resolution - n [bits] 11 10 01 00 set_nelc=
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 25 sx8725 zoomingadc? for pressure and temperature sensing conversion time and throughput as explained in figure 12, conversion time is given by: ( ) s elconv conv f osr n t 1 1 + + = (s) equation 16 and throughput is then simply 1/ t conv . for example, consider an over-sampling ratio of 2 56, 2 elementary conversions, and a over-sampling frequency of 500kh z (set_osr = "101", set_nelc = "01", fin = "00"). i n this case, using table 14, the conversion time is 5 15 over-sampling periods, or 1.03ms. this correspon ds to a throughput of 971hz in continuous-time mode. the pl ot of figure 7 illustrates the classic trade-off be tween resolution and conversion time. set_nelc[1:0] set_osr [2:0] 00 01 10 11 000 10 19 37 73 001 18 35 69 137 010 34 67 133 265 011 66 131 261 521 100 130 259 517 1033 101 258 515 1029 2057 110 514 1027 2053 4105 111 1026 2051 4101 8201 table 14 - normalized conversion time (t conv *f s ) vs. set_osr[2:0] and set_nelc[1:0] (normalized to over-sampling period 1/f s ) note some high sample rate configurations can not be use d due to 2-wire speed limitation. figure 13 - resolution vs. normalized conversion ti me for different set_nelc[1:0] 4.0 6.0 8.0 10.0 12.0 14.0 16.0 10.0 100.0 1000.0 10000.0 normalized conversion time - t conv *f s [-] resolution - n [bits] 00 set_nelc 01 10 11
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 26 sx8725 zoomingadc? for pressure and temperature sensing output code format the adc output code is a 16-bit word in two's compl ement format (see table 15). for input voltages out side the range, the output code is saturated to the closest full-scale value (i.e. 0x7fff or 0x8000). for resol utions smaller than 16 bits, the non-significant bits are forced to the values shown in table 16. the output code, expressed in lsbs, corresponds to: osr osr v v out adc ref adc in adc 1 2 , , 16 + = (lsb) equation 17 recalling equation 9, this can be rewritten as: osr osr v v gdoff gd v v out in adc ref tot tot adc ref in adc 1 2 , , 16 + ? ?? ? ? ?? ? - = (lsb) equation 18 where, from equation 10and equation 11, the total p ga gain and offset are respectively: 1 2 3 gd gd gd gd tot = (v/v) and: 2 3 3 gdoff gd gdoff gdoff tot + = (v/v) adc input voltage v in,adc % of full scale (fs) output in lsbs output code in hex +2.46146v +0.5 fs +215-1=+32'767 7fff +2.46138v ... +215-2=+32'766 7ffe ... ... ... ... +75v ... +1 0001 0v 0 0 0000 -75v ... -1 8fff ... ... ... ... -2.46146v ... -215-1=-32'767 8001 -2.46154v -0.5 fs -215=-32'768 8000 table 15 - basic adc relationships (example for: v ref,adc = 5v, osr = 64, n = 16 bits) set_osr[2:0] set_nelc = 00 set_nelc = 01 set_nelc = 10 set_nelc = 11 000 1000000000 100000000 10000000 1000000 001 10000000 1000000 100000 10000 010 100000 10000 1000 100 011 1000 100 10 1 100 10 1 - - 101 - - - - 110 - - - - 111 - - - - table 16 - last forced lsbs in conversion output re gisters for resolution settings smaller than 16 bits (n < 16) (regacoutmsb[7:0] & regacoutlsb[7:0])
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 27 sx8725 zoomingadc? for pressure and temperature sensing the equivalent lsb size at the input of the pga cha in is: 1 2 1 , + = osr osr gd v lsb tot adc ref n (v) equation 19 notice that the input voltage v in,adc of the adc must satisfy the condition: ( ) 1 2 1 , + - osr osr v v v refn refp adc in (v) equation 20 to remain within the adc input range. power saving modes during low-speed operation, the bias current in the pgas and adc can be programmed to save power using the control words ib_amp_pga[1:0] and ib_amp_adc[1: 0] (see table 17). if the system is idle, the pgas and adc can even be disabled, thus, reducing power cons umption to its minimum. this can considerably impro ve battery life. ib_amp_adc[1:0] (regaccfg1[7:6]) ib_amp_pga[1:0] (regaccfg1[5:4]) adc bias current pga bias current max. f s [khz] 00 1/4 iadc 125 01 1/2 iadc 250 11 x iadc x 500 00 1/4 ipga 125 01 1/2 ipga 250 x 11 x ipga 500 table 17 - adc & pga power saving modes and maximum sampling frequency
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 28 sx8725 zoomingadc? for pressure and temperature sensing registers map address register bits description rc register 0x30 regrcen 1 rc oscillator control gpio registers 0x40 regout 8 d0 to d3 pads data output and directi on control 0x41 regin 4 d0 to d3 pads input data adc registers 0x50 regacoutlsb 8 lsb of the adc result 0x51 regacoutmsb 8 msb of the adc result 0x52 regaccfg0 7 adc conversion control 0x53 regaccfg1 8 adc conversion control 0x54 regaccfg2 8 adc conversion control 0x55 regaccfg3 8 adc conversion control 0x56 regaccfg4 7 adc conversion control 0x57 regaccfg5 8 adc conversion control mode register 0x70 regmode 6 chip operating mode register registers descriptions the register descriptions are presented here in asc ending order of register address. some registers ca rry several individual data fields of various sizes; fr om single-bit values (e.g. flags), upwards. some da ta fields are spread across multiple registers. unused bits are don't care and writing either 0 or 1 will not affe ct any function of the device. after power on reset the registers w ill have the values indicated in the tables reset column. rc register bit name mode reset description 7:1 - r 000000 unused 0 rc_en rw 1 enables rc oscillator. set 0 for low p ower mode. table 18 - regrcen (0x30)
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 29 sx8725 zoomingadc? for pressure and temperature sensing gpio registers bit name mode reset description 7:6 - r 00 unused 5 d1_dir rw 1 d1 pad direction: 1 = output 0 = input 4 d0_dir rw 1 d0 pad direction: 1 = output 0 = input 3:2 - r 00 unused 1 d1_out rw 0 d1 pad output value. only valid when d1_dir = 1 and vref_d1_in = 0 0 d0_out rw 0 d0 pad output value. only valid when d0_dir = 1 and vref_d0_out = 0 table - 19 regout (0x40) bit name mode reset description 7:2 - r 000000 unused 1 d1_in r - d1 pad value 0 d0_in r - d0 pad value table - 20 regin (0x41)
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 30 sx8725 zoomingadc? for pressure and temperature sensing zadc registers bit name mode reset description 7:0 out[7:0] r 00000000 lsb of the adc result table 21 - regacoutlsb (0x50) bit name mode reset description 7:0 out[15:8] r 00000000 msb of the adc result table 22 - regacoutmsb (0x51) bit name mode reset description 7 start rw 0 starts an adc conversion 6:5 set_nelc[1:0] rw 01 sets the number of elementa ry conversions 4:2 set_osr[2:0] rw 010 sets the adc over-sampling rate 1 cont rw 0 sets continuos adc conversion mode 0 - r 0 unused table 23 - regaccfg0 (0x52) bit name mode reset description 7:6 ib_amp_adc[1:0] rw 11 bias current selection fo r the adc 5:4 ib_amp_pga[1:0] rw 11 bias current selection fo r the pga 3:0 enable[3:0] rw 0000 adc and pga stage enables table 24 - regaccfg1 (0x53) bit name mode reset description 7:6 fin[1:0] rw 00 adc sampling frequency selection 5:4 pga2_gain[1:0] rw 00 pga2 gain selection 3:0 pga2_offset[3:0] rw 0000 pga2 offset selection table 25 - regaccfg2 (0x54) bit name mode reset description 7 pga1_gain rw 0 pga1 gain selection 6:0 pga3_gain[6:0] rw 0001100 pga3 gain selection table 26 - regaccfg3 (0x55) bit name mode reset description 7 - 6:0 pga3_offset[6:0] rw 0000000 pga3 offset selecti on table 27 - regaccfg4 (0x56) bit name mode reset description 7 busy r 0 adc activity flag 6 def rw 0 selects adc & pga default configuration 5:1 amux[4:0] rw 00000 input channel configuration selector 0 vmux rw 0 reference source selector (v batt = 0 or v ref = 1) table 28 - regaccfg5 (0x57)
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 31 sx8725 zoomingadc? for pressure and temperature sensing mode register bit name mode reset function 7 mult_ready r 1 1: indicates that the charge pump has settled and t he output voltage is sufficient for conversion 6 mult_active r 0 1: indicates that the charge pump is running (eithe r because vbatt<3v or it has been forced on) 5:4 chop rw 00 vref chopping control 11: chop at nelconv/2 rate 10: chop at nelconv rate 01: chop state = 1 00: chop state = 0 (note 1) 3 mult_force_on rw 0 force charge pump on (takes p riority) (note 2) 2 mult_force_off rw 1 force charge pump off (note 2 ) 1 vref_d0_out rw 0 enable vref output on d0 pin 0 vref_d1_in rw 0 enable vref input on d1 pin note1: the chop control is to allow chopping of the internal bandgap reference. this may be useful to help eliminate bandgap related internal offset voltage and 1/f noise. the bandgap chop state may be forced high or low, or ma y be set to toggle during conversion at either the same rate or half t he rate of the elementary conversion. (see conversi on sequence in the zoomingadc description) note2: the internal charge pump may be forced on or off to avoid conversion interruptions due to the p ump switching off and on when the v batt supply is near 3v. if the pump is on automatic, th en it will activate when v batt drops below 3v to ensure sufficient supply to the adc. if the adc is not bei ng run at full rate or full accuracy then it may op erate sufficiently well when v batt is less than 3v. table 29 - regmode (0x70)
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 32 sx8725 zoomingadc? for pressure and temperature sensing optional operating modes: external voltage referenc e option d0 and d1 are multi-functional pins with the follow ing functions in different operating modes (see regmode register for control settings): figure 14 - d0 and d1 are digital inputs / outputs figure 15 - d0 is digital input / output and d1 reference voltage input figure 16 - d0 is reference voltage output and d1 is digital input / output figure 17 - d0 is reference voltage output and d1 is reference voltage input this allows external monitoring of the internal ban dgap reference or the ability to use an external re ference input for the adc, or the option to filter the internal v ref output before feeding back as v ref,adc input. the internally generated v ref is a trimmed bandgap reference with a nominal valu e of 1.22v. when using an external v ref,adc input, it may have any value between 0v and v batt . simply substitute the external value for 1.22 v in the adc conversion calculations. v ref + - d1/ref in d0/ref out regmode[0] = 0 01 regmode[1] = 0 01 0 1 gpio zoomingadc gpio v ref + - d1/ref in d0/ref out regmode[0] = 1 01 regmode[1] = 0 01 0 1 gpio zoomingadc gpio v ref + - d1/ref in d0/ref out regmode[0] = 0 01 regmode[1] = 1 01 0 1 gpio zoomingadc gpio v ref + - d1/ref in d0/ref out regmode[0] = 1 01 regmode[1] = 1 01 0 1 gpio zoomingadc gpio
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 33 sx8725 zoomingadc? for pressure and temperature sensing application hints recommended operation mode and registers settings operation mode parameter value units analog multiplexers vmux vbatt amux vinp = ac3 & vinn = ac2 pga pga1 gain off v/v pga2 gain off v/v pga3 gain 1 v/v total offset 0 v/v pga2 offset off v/v pga3 offset 0 v/v adc bias 50 % pga bias 50 % adc fs 250 khz resolution 16 bits osr 512 oversamples / elementaryconversion nelconv 2 elementaryconversion / conversion continuous mode on - table 30 - recommended operation mode values registers settings bit position register name 7 6 5 4 3 2 1 0 hexadecimal value regacoutlsb out[7:0] xxxxxxxx regacoutmsb out[15:8] xxxxxxxx regaccfg0 start 0 set_nelc[1:0] 01 set_osr[2:0] 110 cont 1 - 0 0x3a regaccfg1 ib_amp_adc[1:0] 01 ib_amp_pga[1:0] 01 enable[3:0] 1001 0x59 regaccfg2 fin[1:0] 10 pga2_gain[1:0] pga2_offset[3:0] 0000 0x80 regaccfg3 pga1_g 0 pga3_gain[6:0] 0001100 0x0c regaccfg4 - 0 pga3_offset[6:0] 0000000 0x00 regaccfg5 busy 0 def 0 amux[4:0] 00001 vmux 0 0x02 table 31 - registers settings
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 34 sx8725 zoomingadc? for pressure and temperature sensing schematic figure 18 - recommended operation mode schematic signalmux refmux
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 35 sx8725 zoomingadc? for pressure and temperature sensing input impedance the pgas of the zoomingadc are a switched capacitor based blocks (see switched capacitor principle chapter). this means that it does not use resistors to fix gains, but capacitors and switches. this ha s important implications on the nature of the input impedance o f the block. using switched capacitors is the reason why, while a conversion is done, the input impedance on the se lected channel of the pgas is inversely proportional to th e sampling frequency f s and to stage gain as given in equation 21. gain f hz z s in w 3 9 10 768 ( ) equation 21 the input impedance observed is the input impedance of the first pga stage that is enabled or the inpu t impedance of the adc if all three stages are disabl ed. pga1 (with a gain of 10), pga2 (with a gain of 10) and pga3 (with a gain of 10) each have a minimum in put impedance of 150 k at f s = 500 khz (see zoomingadc specifications). larger input impedance can be obtained by reducing the gain and/or by reducing th e sampling frequency. therefore, with a gain of 1 a nd a sampling frequency of 125 khz, z in > 6.1m . the input impedance on channels that are not select ed is very high (>100m ).
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 36 sx8725 zoomingadc? for pressure and temperature sensing switched capacitor principle basically, a switched capacitor is a way to emulate a resistor by using a capacitor. the capacitors ar e much easier to realize on cmos technologies and they sho w a very good matching precision. figure 19 - the switched capacitor principle a resistor is characterized by the current that flo ws through it (positive current leaves node v 1 ): r v v i 2 1 - = (a) equation 22 one can verify that the mean current leaving node v 1 with a capacitor switched at frequency f is: ( ) c f v v i - = 2 1 (a) equation 23 therefore as a mean value, the switched capacitor c f 1 is equivalent to a resistor. it is important to consider that this is only a mea n value. if the current is not integrated (low impe dance source), the impedance is infinite during the whole time but the transition. what does it mean for the zoomingadc? if the f s clock is reduced, the mean impedance is increased. by dividing the f s clock by a factor 10, the impedance is increased by a factor 10. one can reduce the capacitor that is switched by us ing an amplifier set to its minimal gain. in partic ular if pga1 is used with gain 1, its mean impedance is 10x bigg er than when it is used with gain 10. figure 20 - the switched capacitor principle one can increase the effective impedance by increas ing the electrical bandwidth of the sensor node so that the switching current is absorbed through the sensor be fore the switching period is over. measuring the se nsor node will show short voltage spikes at the frequenc y f s , but these will not influence the measurement. whe reas if the bandwidth of the node is lower, no spikes wi ll arise, but a small offset can be generated by th e integration of the charges generated by the switched capacitors , this corresponds to the mean impedance effect. note : one can increase the mean input impedance of the zo omingadc by lowering the acquisition clock f s . one can increase the mean input impedance of the zo omingadc by decreasing the gain of the first enable d amplifier. one can increase the effective input impedance of t he zoomingadc by having a source with a high electr ical bandwidth (sensor electrical bandwidth much higher than f s ). sensor c zoomingadc (model) v 1 f f v 2 sensor impedence node capacitance current integration v 1 v 2 r v 1 f f v 2
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 37 sx8725 zoomingadc? for pressure and temperature sensing pga settling or input channel modifications pgas are reset after each writing operation to regi sters regaccfg1-5 . similarly, input channels are switched after modifications of amux[4:0] or vmux. to ensure precise conversion, the adc must be started after a pga or inputs common-mode stabilization delay. this is done by writing bit start several cycles after pga settings modification or channel switching. delay between pg a start or input channel switching and adc start sh ould be equivalent to osr (between 8 and 1024) number of cy cles. this delay does not apply to conversions made without the pgas. if the adc is not settled within the specified peri od, there is most probably an input impedance probl em (see previous section). pga gain & offset, linearity and noise hereafter are a few design guidelines that should b e taken into account when using the zoomingadc ? : 1. keep in mind that increasing the overall pga gai n, or "zooming" coefficient, improves linearity but degrades noise performance. 2. use the minimum number of pga stages necessary t o produce the desired gain ("zooming") and offset. bypass unnecessary pgas. 3. put most gain on pga3 and use pga2 and pga1 only if necessary. 4. pga3 should be always on for best linearity. 5. for low-noise applications where power consumpti on is not a primary concern, maintain the largest b ias currents in the pgas and in the adc; i.e. set ib_am p_pga[1:0] = ib_amp_adc[1:0] = '11'. 6. for lowest output offset error at the output of the adc, bypass pga2 and pga3. indeed, pga2 and pga3 typically introduce an offset of about 5 to 10 lsb (16 bit) at their output. note, however, that the adc output offset is easily calibrated out by softw are.
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 38 sx8725 zoomingadc? for pressure and temperature sensing frequency response the incremental adc is an over-sampled converter wi th two main blocks: an analog modulator and a low-p ass digital filter. the main function of the digital fi lter is to remove the quantization noise introduced by the modulator. this filter determines the frequency res ponse of the transfer function between the output o f the adc and the analog input v in . notice that the frequency axes are normalized to one elementary conversion period osr / f s . the plots of figure 21 also show that the frequen cy response changes with the number of elementary conversions n elconv performed. in particular, notches appear for n elconv 3 2. these notches occur at: elconv s notch n osr f i i f = )( (hz) for )1 ( ,..., 2,1 - = elconv n i equation 24 and are repeated every f s / osr. information on the location of these notches is par ticularly useful when specific frequencies must be filtered out by the acquisition system. this chip has no dedicat ed 50/60 hz rejection filtering but some rejection can be achieved by using equation 24 and setting the appro priate values of osr, f s and nelconv . examples: rejection [hz] f notch [hz] f s [khz] osr [-] n elconv [-] 61 125 1024 2 61 250 1024 4 60 61 500 1024 8 53 62.5 1024 8 46 62.5 1024 4 50 46 125 1024 8 table 32 - 60/50 hz line rejection examples figure 21 - frequency response: normalized magnitud e vs. frequency for different n elconv 0 0.2 0.4 0.6 0.8 1 1.2 0 1 2 3 4 normalized frequency - f *(osr/f s ) [-] normalized magnitude [-] n elconv = 1 0 0.2 0.4 0.6 0.8 1 1.2 0 1 2 3 4 normalized frequency - f *(osr/f s ) [-] normalized magnitude [-] n elconv = 2 0 0.2 0.4 0.6 0.8 1 1.2 0 1 2 3 4 normalized frequency - f *(osr/f s ) [-] normalized magnitude [-] n elconv = 4 0 0.2 0.4 0.6 0.8 1 1.2 0 1 2 3 4 normalized frequency - f *(osr/f s ) [-] normalized magnitude [-] n elconv = 8
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 39 sx8725 zoomingadc? for pressure and temperature sensing power reduction the zoomingadc ? is particularly well suited for low-power applicat ions. when very low power consumption is of primary concern, such as in battery operated sys tems, several parameters can be used to reduce powe r consumption as follows: 1. operate the acquisition chain with a reduced sup ply voltage vdd. 2. disable the pgas which are not used during analo g-to-digital conversion with enable[3:0]. 3. disable all pgas and the adc when the system is idle and no conversion is performed. 4. use lower bias currents in the pgas and the adc using the control words ib_amp_pga[1:0] and ib_amp_adc[1:0]. 5. reduce sampling frequency. finally, remember that power reduction is typically traded off with reduced linearity, larger noise an d slower maximum sampling speed. recommended design for other 2-wire devices connect ion sx8725 does not support multiple devices on the sam e 2-wire bus. a separate 2-wire bus should be used to address other devices as seen on the following sche matic. sx8725 ac2 ac3 d0 d1 vbatt vpump vss ready scl sda uc scl1 sda1 i2c1 i2c2 eeprom (orother devices) a0 a1 a2 gnd vcc scl2 sda2 vcc gnd figure 22 - recommended connections with other devi ces
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 40 sx8725 zoomingadc? for pressure and temperature sensing typical performance note: the graphs and tables provided following this note are statistical summary based on limited number of samples and are provided for informational purposes only. the performance characteristics listed herei n are not tested or guaranteed. in some graphs or tables, the data presented may be outside the specified operat ing range and therefore outside the warranted range. linearity integral non-linearity the different pga stages have been designed to find the best compromise between the noise performance, the integral non-linearity and the power consumption. t o obtain this, the first stage has the best noise p erformance and the third stage the best linearity performance. for large input signals (small pga gains, i.e. up to about 50), the noise added by the pga is very small with respe ct to the input signal and the second and third sta ge of the pga should be used to get the best linearity. for s mall input signals (large gains, i.e. above 50), th e noise level in the pga is important and the first stage of the pga should be used. the following figures show the integral non lineari ty for different gain settings over the chip temper ature range. gain 1 -40 c 25 c 85 c 125 c
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 41 sx8725 zoomingadc? for pressure and temperature sensing gain 10 -40 c 25 c 85 c 125 c gain 100 -40 c 25 c 85 c 125 c
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 42 sx8725 zoomingadc? for pressure and temperature sensing gain 1000 -40 c 25 c 85 c 125 c
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 43 sx8725 zoomingadc? for pressure and temperature sensing differential non-linearity the differential non-linearity is generated by the adc. the pga does not add differential non-linearit y. figure 23 shows the differential non-linearity. figure 23 - differential non-linearity of the adc c onverter
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 44 sx8725 zoomingadc? for pressure and temperature sensing noise ideally, a constant input voltage vin should result in a constant output code. however, because of cir cuit noise, the output code may vary for a fixed input voltage. thus, a statistical analysis on the output code of 1200 conversions for a constant input voltage was perfor med to derive the equivalent noise levels of pga1, pga2, and pga3. the extracted rms output noise of pga1, 2 , and 3 are given in table 33: standard output devi ation and output rms noise voltage. figure 24 shows the d istribution for the adc alone (pga1, 2, and 3 bypas sed). quantization noise is dominant in this case, and, t hus, the adc thermal noise is below 16 bits. the simple noise model of figure 25 is used to esti mate the equivalent input referred rms noise v n,in of the acquisition chain in the model of figure 26. this i s given by the relationship: ( ) elconv n n n in n n osr gd gd gd v gd gd v gd v v ? ?? ? ? ?? ? + ? ?? ? ? ?? ? + ? ?? ? ? ?? ? = 2 3 2 1 3 2 2 1 2 2 1 1 2 , (v 2 rms) equation 25 where v n1 , v n2 , and v n3 are the output rms noise figures of table 33, gd 1 , gd 2 , and gd 3 are the pga gains of stages 1 to 3 respectively. as shown in this equati on, noise can be reduced by increasing osr and n elconv (increases the adc averaging effect, but reduces no ise). parameter pga1 pga2 pga3 standard deviation at adc output (lsb) 0.85 1.4 1.5 output rms noise (v) 205 (v n1 ) 340 (v n2 ) 365 (v n3 ) table 33 - pga noise measurements (n = 16 bits, osr = 512, n elconv = 2, v ref = 5 v)
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 45 sx8725 zoomingadc? for pressure and temperature sensing figure 24 - adc noise (pga1, 2 & 3 bypassed, osr = 512, n elconv = 2) figure 25 - simple noise model for pgas and adc figure 26 - total input referred noise as an example, consider the system where: gd 2 = 10 (gd 1 = 1; pga3 bypassed), osr = 512, n elconv = 2, v ref = 5 v. in this case, the noise contribution v n1 of pga1 is dominant over that of pga2. using equat ion 25, we get: v n,in = 6.4 v (rms) at the input of the acquisition cha in, or, equivalently, 0.85 lsb at the output of the adc. considering 0.2 v (rms) maximum signal amplitu de, the signal-to-noise ratio is 90db. noise can also be reduced by implementing a softwar e filter. by making an average on a number of subse quent measurements, the apparent noise is reduced the squ are root of the number of measurement used to make the average. 0 20 40 60 80 -5 -4 -3 -2 -1 0 1 2 3 4 5 output code deviation from mean value [lsb] occurences [% of total samples] gd1 gd2 gd3 adc f s v n1 v n2 v n3 pga1 pga2 pga3 gd1 gd2 gd3 adc f s v n1 v n2 v n3 pga1 pga2 pga3 v n,in
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 46 sx8725 zoomingadc? for pressure and temperature sensing gain error and offset error gain error is defined as the amount of deviation be tween the ideal transfer function (theoretical equa tion 18) and the measured transfer function (with the offset error removed). the actual gain of the different stages can vary de pending on the fabrication tolerances of the differ ent elements. although these tolerances are specified t o a maximum of 3%, they will be most of the time around 0.5%. moreover, the tolerances between the differen t stages are not correlated and the probability to get the maximal error in the same direction in all stages i s very low. finally, these gain errors can be calib rated by the software at the same time with the gain errors of t he sensor for instance. figure 27 shows gain error drift vs. temperature fo r different pga gains. the curves are expressed in % of full- scale range (fsr) normalized to 25c. offset error is defined as the output code error fo r a zero volt input (ideally, output code = 0). the offset of the adc and the pga1 stage are completely suppressed if nelconv > 1. the measured offset drift vs. temperature curves fo r different pga gains are depicted in figure 28. th e output offset error, expressed in lsb for 16-bit setting, is normalized to 25c. notice that if the adc is us ed alone, the output offset error is below 1 lsb and has no drift. normalized to 25c figure 27 - gain error vs. temperature for differen t pga gains normalized to 25c figure 28 - offset error vs. temperature for differ ent pga gains -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 -50 -25 0 25 50 75 100 temperature [c] gain error [% of fsr] 1 5 20 100 -40 -20 0 20 40 60 80 100 -50 -25 0 25 50 75 100 temperature [c] output offset error [lsb] 1 5 20 100
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 47 sx8725 zoomingadc? for pressure and temperature sensing power consumption figure 29 plots the variation of quiescent current consumption with supply voltage v dd , as well as the distribution between the 3 pga stages and the adc ( see table 34). as shown in figure 30, if lower samp ling frequency is used, the quiescent current consumptio n can be lowered by reducing the bias currents of t he pgas and the adc with registers ib_amp_pga [1:0] and ib_ amp_adc [1:0]. (in figure 30, ib_amp_pga/adc[1:0] = '11', '10', '00' for f s = 500, 250, 62.5 khz respectively.) quiescent current consumption vs. temperature is de picted in figure 31, showing a relative increase of nearly 40% between -45 and +85c. figure 29 - quiescent current consumption vs. suppl y voltage figure 30 - quiescent current consumption vs. suppl y voltage for different sampling frequencies
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 48 sx8725 zoomingadc? for pressure and temperature sensing figure 31 - absolute change in quiescent current co nsumption vs. temperature figure 32 - relative change in quiescent current co nsumption vs. temperature supply back bone adc pga1 pga2 pga3 total unit v dd = 5 v 142 127 96 86 97 548 v dd = 3.3 v 98 105 87 73 96 459 v dd = 2.5 v 99 105 87 71 91 453 a table 34 - typical quiescent current distributions in acquisition chain (n = 16 bits, f s = 250 khz)
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 49 sx8725 zoomingadc? for pressure and temperature sensing pcb layout considerations pcb layout considerations to be taken when using th e sx8725 are relatively simple to get the highest performances out of the zoomingadc. the most import ant to achieve good performances out the zoomingadc is to have a good voltage reference. the sx8725 has already an internal reference that is good enough to get the best performances with a minimal amount of exte rnal components, but, in case an external reference is needed this one must be as clean as possible in ord er to get the desired performance. separating the d igital from the analog lines will be also a good choice to reduce the noise induced by the digital lines. it is also advised to have separated ground planes for digital and analog signals with the shortest return path, as well as making the power supply lines as wider as possible and to have good decoupling capacitors. how to evaluate the sx8725 is a subset of the sx8724 thus for evalu ation purposes the xe8000ev121 evaluation kit can b e ordered. this kit connects to any pc using a usb po rt. the sx87xx evaluation tools software gives th e user the ability to control the sx8724 registers as well as getting the raw data from the zoomingadc and di splaying it on the graphical user interface. for more info rmation please look at semtech web site ( http://www.semtech.com ).
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 50 sx8725 zoomingadc? for pressure and temperature sensing package outline drawing: mlpd-w-12 4x4
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 51 sx8725 zoomingadc? for pressure and temperature sensing land pattern drawing: mlpd-w-12 4x4
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 52 sx8725 zoomingadc? for pressure and temperature sensing tape and reel specification mlp/qfn (0.70mm - 1.00mm package thickness) 1. single sprocket holes 2. tolerances for ao & bo are +/- 0.20mm 3. tolerances for ko is +/- 0.10mm 4. tolerance for pocket pitch is +/- 0.10mm 5. tolerance for tape width is +/-0.30mm 6. trailer and leader length are minimum required l ength 7. package orientation and feed direction 8. tape and reel dimensions carrier tape (mm) reel pkg size tape width (w) pocket pitch (p) ao bo ko reel size (in) reel width (mm) trailer length (mm) leader length (mm) qty per reel 2.0x2.0 8 4 2.25 2.25 1.00 7 8.4 160 400 3000 2.3x2.3 12 8 2.60 2.60 1.00 13 12.4 400 400 3000 3x3 12 8 3.30 3.30 1.10 13 12.4 400 400 3000 4x4 12 8 4.35 4.35 1.10 7/13 12.4 400 400 1000/3000 4x3 12 8 3.30 4.30 1.10 13 12.4 400 400 3000 5x5 12 8 5.25 5.25 1.10 7/13 12.4 200/400 400 500/3 000 6x6 16 12 6.30 6.30 1.10 13 16.4 400 400 3000 6x5 12 8 5.30 6.30 1.10 13 12.4 400 400 3000 7x7 16 12 7.30 7.30 1.10 13 16.4 400 400 3000 9x9 16 12 9.30 9.30 1.10 13 16.4 400 400 3000 10x10 24 16 10.30 10.30 1.10 13 24.4 400 400 3000 11x11 24 16 11.40 11.40 1.20 13 24.4 400 400 3000
advanced communications & sensing v1.8 ? 2009 semtech corp. www.semtech.com 53 sx8725 zoomingadc? for pressure and temperature sensing contact information ? semtech 2009 all rights reserved. reproduction in whole or in par t is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believe d to be accurate and reliable and may be changed without notice. no liab ility will be accepted by the publisher for any co nsequence of its use. publication thereof does not convey nor imply any li cense under patent or other industrial or intell ectual property rights. semtech assumes no responsibility or liability whats oever for any failure or unexpected operation resul ting fr om misuse, neglect improper installation, repair or improper h andling or unusual physical or electrical stress in cluding, 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 applicat ions. inclusion of semtech products in such applications is understood to be un dertaken s olely at the customers own risk. should a customer purchase or use se mtech products for any such unauthorized applicatio n, the customer shall indemnify and hold semtech and it s officers, employees, subsidiaries, affiliates, an d distributors harmless again st all claims, costs damages and attorney fees whic h could arise. semtech corporation advanced communication and sensing products divisio n 200 flynn road, camarillo, ca 93012 phone (805) 498-2111 fax : (805) 498-3804

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