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preliminary product information this document contains information for a new product. cirrus logic reserves the right to modify this product without notice. copyright ? cirrus logic, inc. 2008 (all rights reserved) http://www.cirrus.com 3/25/08 10:56 cs5571 2.5 v / 5 v, 100 ksps, 16-bit, high-throughput ? adc features & description ? single-ended analog input ? on-chip buffers for high input impedance ? conversion time = 10 s ? settles in one conversion ? linearity error = 0.0008% ? signal-to-noise = 92 db ? s/(n + d) = 91 db ? dnl = 0.1 lsb max. ? simple three/four-wire serial interface ? power supply configurations: - analog: +5v/gnd; io: +1.8v to +3.3v - analog: 2.5v; io : +1.8v to +3.3v ? power consumption: - adc input buffers on: 85 mw - adc input buffers off: 60 mw general description the cs5571 is a single-channel, 16-bit analog-to-digital converter capable of 100 ksps conversion rate. the input accepts a single-ended analog input signal. on-chip buff- ers provide high input impedance for both the ain input and the vref+ input. this significantly reduces the drive requirements of signal sources and reduces errors due to source impedances. the cs5571 is a delta-sigma convert- er capable of switching multiple input channels at a high rate with no loss in throughput. the adc uses a low-laten- cy digital filter architecture. the filter is designed for fast settling and settles to full accuracy in one conversion. the converter's 16-bit data output is in serial format, with the serial port acting as either a master or a slave. the convert- er is designed to support bipolar, ground-referenced signals when operated from 2.5v analog supplies. the converter can operate from an analog supply of 0-5v or from 2.5v. the digital interface supports standard logic operating from 1.8, 2.5, or 3.3 v. ordering in formation: see ordering information on page 34. ain acom cs sclk smode vref+ vref- rdy osc/clock generator conv bp/up digital control serial interface adc digital filter logic vl mclk sdo rst dither dcr vlr v1- v2- bufen v2+ v1+ cs5571 tst vlr2 mar ?08 ds768pp1
cs5571 2 ds768pp1 3/25/08 10:56 table of contents 1. characteristics and spec ifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 analog characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 switching characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 digital characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 guaranteed logic levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3. theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.1 converter operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 3.2 clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 voltage reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 3.4 analog input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.5 output coding format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 3.6 typical connection diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.7 ain & vref sampling structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.8 converter performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 0 3.9 dither . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.10 digital filter characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.11 serial port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.11.1 ssc mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.11.2 sec mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.12 power supplies & grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.13 using the cs5571 in multiplexing applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.14 synchronizing multiple converters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4. pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 5. package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 6. ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 7. environmental, manufact uring, & handling information . . . . . . . . . . . . . . 34 8. revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
cs5571 ds768pp1 3 3/25/08 10:56 list of figures figure 1. ssc mode - read timing, cs remaining low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 figure 2. ssc mode - read timing, cs falling after rdy falls . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 3. sec mode - continuous sclk read timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 4. sec mode - discontinuous sclk read timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 5. voltage reference circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 figure 6. cs5571 configured using 2.5v analog supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 7. cs5571 configured for unipolar measurement using a single 5v analog supply . . . . 18 figure 8. cs5571 configured for bipolar measurement using a single 5v analog supply . . . . . 19 figure 9. cs5571 dnl plot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 10. cs5581 dnl error plot with dnl histogram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 11. spectral performance, 0 db. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 figure 12. spectral performance, -6 db . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 figure 13. spectral performance, -12 db . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 14. spectral performance, -80 db dither on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 15. spectral performance, -80 db dither off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 16. spectral performance, -100 db dither on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 17. spectral performance, -100 db dither off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 18. spectral performance, -116.3 db dither on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 19. spectral plot of noise with shorted input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 20. noise histogram, 4096 samp les dither on, code center. . . . . . . . . . . . . . . . . . . . . . 24 figure 21. noise histogram, 4096 samp les dither off, code center. . . . . . . . . . . . . . . . . . . . . . 24 figure 22. noise histogram, 4096 sa mples dither on, input at code boundary . . . . . . . . . . . . . 24 figure 23. noise histogram, 4096 sa mples dither off, input at code boundary . . . . . . . . . . . . . 24 figure 24. cs5571 digital filter response (dc to fs/2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 figure 25. cs5571 digital filter response (dc to 10 khz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 figure 26. cs5571 digital filter response (dc to 4fs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 figure 27. simple multiplexing scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 figure 28. more complex multip lexing scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 list of tables table 1. output coding, two?s complement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 table 2. output coding, offset binary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
cs5571 4 ds768pp1 3/25/08 10:56 1. characteristics and specifications ? min / max characteristics and spec ifications are guaranteed over th e specified operating conditions. ? typical characteristics and specifications are measured at nominal supply voltages and t a = 25c. ? vlr = 0 v. all voltages measured with respect to 0 v. analog characteristics t a = -40 to +85 c; v1+ = v2+ = +2.5 v, 5%; v1- = v2- = -2.5 v, 5%; vl -vlr = 3.3 v, 5%; vref = (vref+) - (vref -) = 4.096v; mclk = 16 mhz; smode = vl. dither = vl unless otherwise stated; bufen = v1+ unless otherwise stated. connected per figure 6 . bipolar mode unless oth- erwise stated. 1. no missing codes is guaranteed at 16 bits re solution over the specified temperature range. 2. one lsb is equivalent to vref 2 16 or 4.096 65536 = 62.5 v. 3. total drift over specified temperature range after reset at power-up, at 25o c. 4. with dither off the output will be dominated by quantization. 5. scales with mclk. parameter min typ max unit accuracy linearity error - 0.0008 - %fs differential linearity error (note 1) - - 0.1 lsb 16 positive full-scale error - 1.0 - %fs negative full-scale error - 1.0 - %fs full-scale drift (note 2, 3) - 1 - lsb 16 bipolar offset (note 2) - 15 - lsb 16 bipolar offset drift (note 2, 3) - 1 - lsb 16 noise (note 4) - 36 - vrms dynamic performance peak harmonic or spurious noise 1 khz, -0.5 db input 12 khz, -0.5 db input - - -96 -96 - - db db total harmonic distortion 1 khz, -0.5 db input - -94 -82 db signal-to-noise 91 92 - db s/(n + d) ratio -0.5 db input, 1 khz -60 db input, 1 khz - - 91 32 - - db db -3 db input bandwidth (note 5) - 84 - khz
cs5571 ds768pp1 5 3/25/08 10:56 analog characteristics (continued) t a = -40 to +85 c; v1+ = v2 + = +2.5 v, 5%; v1- = v2- = -2.5 v, 5%; vl -vlr = 3.3 v, 5%; vref = (vref+) - (vref-) = 4.096v; mc lk = 16 mhz; smode = vl. dither = vl unless otherwise stated; bufen = v1 + unless otherwise stated. connected per figure 6 . 6. measured using an input signal of 1 v dc. 7. for optimum performance, vref+ should always be less than (v+) - 0.2 volts to prevent saturation of the vref+ input buffer. 8. tested with 100 mvp-p on any supply up to 1 khz. v1+ and v2+ supplies at the same voltage potential, v1- and v2- supplies at the same voltage potential. parameter min typ max unit analog input analog input range unipolar bipolar 0 to +vref / 2 vref / 2 v v input capacitance - 10 - pf cvf current (note 6) ain buffer on (bufen = v+) ain buffer off (bufen = v-) acom - - - 600 130 130 - - - na a a voltage reference input voltage reference input range (vref+) ? (vref-) (note 7) 2.4 4.096 4.2 v input capacitance - 10 - pf cvf current vref+ buffer on (bufen = v+) vref+ buffer off (bufen = v-) vref- - - - 3 1 1 - - - a ma ma power supplies dc power supply currents i v1 i v2 i vl - - - - - - 18 1.8 0.6 ma ma ma power consumption normal operation buffers on buffers off - - 85 60 101 80 mw mw power supply rejection (no te 8) v1+ , v2+ supplies v1-, v2- supplies - - 80 80 - - db db
cs5571 6 ds768pp1 3/25/08 10:56 switching characteristics t a = -40 to +85 c; v1+ = v2+ = +2.5 v, 5%; v1- = v2- = -2.5 v, 5%; vl - vlr = 3.3 v, 5%, 2.5 v, 5%, or 1.8 v, 5% input levels: logic 0 = 0v = low; logic 1 = vd+ = high; cl = 15 pf. 9. reset must not be released until the power supplies and the voltage reference are within specification. 10. bp/up can be changed coincident to conv falling. bp/up must remain stable until rdy falls. 11. if conv is held low continuously, conversions occur every 160 mclk cycles. if rdy is tied to conv , conversions will occur every 162 mclks. if conv is operated asynchronously to mclk, a conversion may take up to 164 mclks. rdy falls at the end of conversion. parameter symbol min typ max unit master clock frequenc y internal oscillator external clock xin f clk 12 0.5 14 16 16 16.2 mhz mhz master clock duty cycle 40 - 60 % reset rst low time (note 9) t res 1- -s rst rising to rdy falling internal oscillator external clock t wup - - 120 1536 - - s mclks conversion conv pulse width t cpw 4- -mclks bp/up setup to conv falling (note 10) t scn 0- -ns conv low to start of conversion t scn --2mclks perform single conversion (conv high before rdy falling) t bus 20 - - mclks conversion time (note 11) start of conversion to rdy falling t buh --164mclks
cs5571 ds768pp1 7 3/25/08 10:56 switching characteristics (continued) t a = -40 to +85 c; v1+ = v2+ = +2.5 v, 5%; v1- = v2- = -2.5 v, 5%; vl - vlr = 3.3 v, 5%, 2.5 v, 5%, or 1.8 v, 5% input levels: logic 0 = 0v = low; logic 1 = vd+ = high; cl = 15 pf. 12. sdo and sclk will be high impedance when cs is high. in some systems sclk and sdo may require pull-down resistors. 13. sclk = mclk/2. parameter symbol min typ max unit serial port timing in ssc mode (smode = vl) rdy falling to msb stable t 1 --2-mclks data hold time after sclk rising t 2 -10-ns serial clock (out) pulse width (low) (note 12, 13) pulse width (high) t 3 t 4 50 50 - - - - ns ns rdy rising after last sclk rising t 5 -8-mclks mclk rdy sclk(o) sdo msb msb ? 1 lsb lsb+1 cs t 1 t 2 t 3 t 4 t 5 figure 1. ssc mode - read timing, cs remaining low (not to scale)
cs5571 8 ds768pp1 3/25/08 10:56 switching characteristics (continued) t a = -40 to +85 c; v1+ = v2+ = +2.5 v, 5%; v1- = v2- = -2.5 v, 5%; vl - vlr = 3.3 v, 5%, 2.5 v, 5%, or 1.8 v, 5% input levels: logic 0 = 0v = low; logic 1 = vd+ = high; cl = 15 pf. 14. sdo and sclk will be high impedance when cs is high. in some systems sclk and sdo may require pull-down resistors. 15. sclk = mclk/2. parameter symbol min typ max unit serial port timing in ssc mode (smode = vl) data hold time after sclk rising t 7 -10-ns serial clock (out) pulse width (low) (note 14, 15) pulse width (high) t 8 t 9 50 50 - - - - ns ns rdy rising after last sclk rising t 10 -8-mclks cs falling to msb stable t 11 -10-ns first sclk rising after cs falling t 12 -8-mclks cs hold time (low) after sclk rising t 13 10 - - ns sclk, sdo tri-state after cs rising t 14 -5-ns mclk rdy sclk(o) sdo cs t 12 t 8 t 13 t 9 t 7 t 11 msb msb ? 1 lsb lsb+1 t 14 t 10 figure 2. ssc mode - read timing, cs falling after rdy falls (not to scale)
cs5571 ds768pp1 9 3/25/08 10:56 switching characteristics (continued) t a = -40 to +85 c; v1+ = v2+ = +2.5 v, 5%; v1- = v2- = -2.5 v, 5%; vl - vlr = 3.3 v, 5%, 2.5 v, 5%, or 1.8 v, 5% input levels: logic 0 = 0v = low; logic 1 = vd+ = high; cl = 15 pf. 16. sdo will be high impedance when cs is high. in some systems sdo ma y require a pull-down resistor. parameter symbol min typ max unit serial port timing in sec mode (smode = vlr) sclk(in) pulse width (high) - 30 - - ns sclk(in) pulse width (low) - 30 - - ns cs hold time (high) after rdy falling t 15 10 - - ns cs hold time (high) after sclk rising t 16 10 - - ns cs low to sdo out of hi-z (note 16) t 17 -10-ns data hold time after sclk rising t 18 -10-ns data setup time before sclk rising t 19 10 - - ns cs hold time (low) after sclk rising t 20 10 - ns rdy rising after sclk falling t 21 -10-ns 1 sclk 10 mclk sclk(i) sdo cs rdy lsb msb t 19 t 18 t 20 t 17 t 16 t 15 t 21 figure 3. sec mode - continuous sclk read timing (not to scale)
cs5571 10 ds768pp1 3/25/08 10:56 digital characteristics t a = tmin to tmax; vl = 3.3v, 5% or vl = 2.5v, 5% or 1.8v, 5%; vlr = 0v parameter symbol min typ max unit input leakage current i in --2a digital input pin capacitance c in -3-pf digital output pin capacitance c out -3-pf mclk sclk(i) sdo cs rdy lsb msb t 19 t 18 t 20 t 17 t 15 t 21 figure 4. sec mode - discontinuous sclk read timing (not to scale)
cs5571 ds768pp1 11 3/25/08 10:56 guaranteed logic levels t a =-40to+85c;v1+=v2+=+2.5 v, 5%; v1- = v2- = -2.5 v, 5%; vl - vlr = 3.3 v, 5%, 2.5 v, 5%, or 1.8 v, 5% input levels: logic 0 = 0v = low; logic 1 = vd+ = high; cl = 15 pf. guaranteed limits parameter sym vl min typ max unit conditions logic inputs minimum high-level input voltage: v ih 3.3 1.9 v 2.5 1.6 1.8 1.2 maximum low-level input voltage: v il 3.3 1.1 v 2.5 0.95 1.8 0.6 logic outputs minimum high-level output voltage: v oh 3.3 2.9 v i oh =-2ma 2.5 2.1 1.8 1.65 maximum low-level output voltage: v ol 3.3 0.36 v i oh =-2ma 2.5 0.36 1.8 0.44
cs5571 12 ds768pp1 3/25/08 10:56 recommended operating conditions (vlr = 0v, see note 17 ) 17. the logic supply can be any value vl ? vlr = +1.71 to +3.465 volts as long as vlr v2- and vl 3.465 v. 18. the differential voltage reference magnitude is constrained by the v1+ or v1- supply magnitude. absolute maximum ratings (vlr = 0v ) notes: 19. v1+ = v2+; v1- = v2- 20. v1- = v2- 21. transient currents of up to 1 00 ma will not cause scr latch-up. warning: recommended operating conditions indicate limits to which the device is functionally operational. abso- lute maximum ratings indicate limits beyond whic h permanent damage to the device may occur. the absolute maximum ratings are stress ratings only and the device should not be operated at these limits. operation at conditions beyond the recommended operat ing conditions may affect device reliability, and functional operation beyond recommended operating condit ions is not implied. performance specifica- tions are intended for the conditions specified for each table in the characteristics and specifications sec- tion. parameter symbol min typ max unit single analog supply dc power supplies: (note 17) v1+ v2+ v1- v2- v1+ v2- v1+ v2- 4.75 4.75 - - 5.0 5.0 0 0 5.25 5.25 - - v v v v dual analog supplies dc power supplies: (note 17) v1+ v2+ v1- v2- v1+ v2- v1+ v2- +2.375 +2.375 -2.375 -2.375 +2.5 +2.5 -2.5 -2.5 +2.625 +2.625 -2.625 -2.625 v v v v analog reference voltage (note 18) [vref+] ? [vref-] vref 2.4 4.096 4.2 v parameter symbol min typ max unit dc power supplies: [v1+] ? [v1-] (note 19) vl + [ |v1-| ] (note 20) - - 0 0 - - 5.5 6.1 v v input current, any pin ex cept supplies (note 21) i in --10ma analog input voltage (ain and vref pins) v ina (v1-) ? 0.3 - (v1+) + 0.3 v digital input voltage v ind vlr ? 0.3 - vl + 0.3 v storage temperature t stg -65 - 150 c
cs5571 ds768pp1 13 3/25/08 10:56 2. overview the cs5571 is a 16-bit analog-to-digital converter capable of 100 ksps conversion rate. the analog input accepts a single-ended input wi th a magnitude of vref / 2 volts. the device is capable of switching mul- tiple input channels at a high rate with no loss in thr oughput. the adc uses a low-latency digital filter ar- chitecture. the filter is designed for fast settlin g and settles to full accuracy in one conversion. the converter is a serial output device. the serial po rt can be configured to function as either a master or a slave. the converter can operate from an analog supply of 5v or from 2.5v. the digital interface supports stan- dard logic operating from 1.8, 2.5, or 3.3 v. the cs5571 may convert at rates up to 100 ksps when operating from a 16 mhz input clock. 3. theory of operation the cs5571 converter provides high-performance meas urement of dc or ac signals. the converter can be used to perform single conversi ons or continuous conversions upon command. each conversion is in- dependent of previous conver sions and settles to full specified accura cy, even with a full-scale input volt- age step. this is due to the converter architecture which uses a combination of a high-speed delta-sigma modulator and a low-latency filter architecture. once power is established to the converter, a reset must be performed. a reset initializes the internal con- verter logic . if conv is held low, the converter will convert continuously with rdy falling every 160 mclks. this is equivalent to 100 ksps if mclk = 16.0 mhz. if conv is tied to rdy , a conversion will occur every 162 mclks. if conv is operated asynchronously to mclk, it may take up to 164 mclks from conv falling to rdy falling. multiple converters can operate synchronously if they are driven by the same mclk source and conv to each converter falls on the same mclk falling edge. alternately, conv can be held low and all devices can be synchronized if they are reset with rst rising on the same falling edge of mclk. the output coding of the conversion word is a function of the bp/up pin. 3.1 converter operation the converter should be reset after the power supplies and voltage reference are stable. the cs5571 converts at 100 ksps when synchronously operated (conv = vlr) from a 16.0 mhz master clock. conversion is initiated by taking conv low. a conversion lasts 160 master clock cycles, but if conv is asynchronous to mclk there may be an unc ertainty of 0-4 mclk cycles after conv falls to when a conversion actually begins. this may extend the throughput to 164 mclks per conversion. when the conversion is completed, the output word is placed into the serial port and rdy goes low. to convert continuously, conv should be held low. in conti nuous conversion mode with conv held low, a conversion is performed in 160 mclk cycles. alternately rdy can be tied to conv and a conversion will occur every 162 mclk cycles. to perform only one conversion, conv should return high at least 20 master clock cycles before rdy falls.
cs5571 14 ds768pp1 3/25/08 10:56 once a conversion is completed and rdy falls, rdy will return high when all the bits of the data word are emptied from the serial port or if the conversion data is not read and cs is held low, rdy will go high two mclk cycles before the end of conversion. rdy will fall at the end of the next conversion when new data is put into the port register. see serial port on page 26 for information about reading conversion data. conversion performance can be affected by several fact ors. these include the choice of clock source for the chip, the timing of conv , the setting of the dither function, and the choice of the serial port mode. the converter can be operated from an internal oscill ator. this clock source has greater jitter than an external crystal-based clock. jitter may not be an issue when measuring dc signals, or very-low-fre- quency ac signals, but can become an issue for higher frequency ac signals. for maximum performance when digitizing ac signals, a low-jitter mclk should be used. to achieve the highest resolution when measuring a dc signal with a single conversion the dither func- tion should be off. if averaging is to be perform ed with multiple conversions of a dc signal, dither should be on. to maximize performance, the conv pin should be held low in the continuous conversion state to perform multiple conversions, or conv should occur synchronous to mclk, falling when mclk falls. if the converter is operated at maximum throughput, the ssc serial port mode is less likely to cause in- terference to measurements as the sclk output is synchronized to the mclk. alternately, any interfer- ence due to serial port clocking can also be minimize d if data is read in the sec serial port mode when a conversion is not in progress. 3.2 clock the cs5571 can be operated from its internal oscillator or from an external master clock. the state of mclk determines which clock source will be used. if mclk is tied low, the internal oscillator will start and be used as the clock source for the converter. if an external cmos-compatible clock is input into mclk, the converter will power down the internal oscillator and use the external clock. if the mclk pin is held high, the internal oscillator will be held in the stopped state. the mclk input can be held high to delete clock cycles to aid in synchronizing multiple converters in different phase relationships. the internal oscillator can be used if the signals to be measured are essentially dc. the internal oscillator exhibits jitter at about 500 picoseconds rms. if the cs 5571 is used to digitize ac signals, an external low-jitter clock source should be used. if the internal oscillator is used as the clock for t he cs5571, the maximum conversion rate will be dictated by the oscillator frequency. if driven from an external mclk source, the fast rise and fall times of the mclk signal can result in clock coupling from the internal bond wire of the ic to the analog input. adding a 50 ohm resistor on the external mclk source significantly reduces this effect.
cs5571 ds768pp1 15 3/25/08 10:56 3.3 voltage reference the voltage reference for the cs5571 can range from 2.4 volt to 4.2 volts. a 4.096 volt reference is re- quired to achieve the specified signal-to-noise performance. figure 6 and figure 7 illustrate the connec- tion of the voltage reference with either a single +5 v analog supply or with 2.5 v. for optimum performance, the voltage reference device should be one that provides a capacitor connec- tion to provide a means of noise filt ering, or the output should include so me type of bandwidth-limiting fil- ter. some 4.096 volt reference devices need only 5 volts total supply for operation and can be connected as shown in figure 6 or figure 7 . the reference should have a local bypass capacitor and an appropriate output capacitor. some older 4.096 voltage reference designs require more headroom and must operate from an input volt- age of 5.5 to 6.5 volts. if this type of voltage reference is used ensure that when power is applied to the system, the voltage reference rise time is slower than the rise time of the v1+ and v1- power supply volt- age to the converter. an example circuit to slow the output startup time of the reference is illustrated in figure 5 . figure 5. voltage reference circuit 3.4 analog input the analog input of the converter is single-ended with a full-scale input of 2.048 volts, relative to the acom pin.. this is illustrated in figure 6 and figure 7 . these diagrams also illustrate a differential buffer amplifier configuration for driving the cs5571. the capacitors at the outputs of the amplifiers provide a charge reservoir for the dynamic current from the a/d inputs while the resistors isolate the dynamic curr ent from the amplifier. the amplifiers can be pow- ered from higher supplies than those used by the a/d but precautions should be taken to ensure that the op-amp output voltage remains within the power supply limits of the a/d, espec ially under start-up condi- tions. 2k 10 f 5.5 to 15 v vin vout gnd 4.096 v refer to v1- and vref1 pins.
cs5571 16 ds768pp1 3/25/08 10:56 3.5 output coding format the reference voltage directly defines the input voltage range in both the unipolar and bipolar configura- tions. in the unipolar configuration (bp/up low), the first code transition oc curs 0.5 lsb above zero, and the final code transition occurs 1.5 lsbs below vref. in the bipolar configuration (bp/up high), the first code transition occurs 0.5 lsb above -vref and the last transition occurs 1.5 lsbs below +vref. see table 1 for the output coding of the converter. note: vref = [(vref+) - (vref-)] / 2 table 1. output coding, two?s complement bipolar input voltage two?s complement >(vref-1.5 lsb) 7f ff vref-1.5 lsb 7f ff 7f fe -0.5 lsb 00 00 ff ff -vref+0.5 lsb 80 01 80 00 <(-vref+0.5 lsb) 80 00 note: vref = [(vref+) - (vref-)] / 2 table 2. output c oding, offset binary unipolar input voltage offset binary >(vref-1.5 lsb) ff ff vref-1.5 lsb ff ff ff fe (vref/2)-0.5 lsb 80 00 7f ff +0.5 lsb 00 01 00 00 <(+0.5 lsb) 00 00
cs5571 ds768pp1 17 3/25/08 10:56 3.6 typical connection diagrams the following figure depicts the cs5571 powered from bipolar analog supplies, +2.5 v and - 2.5 v. figure 6. cs5571 configured using 2.5v analog supplies vref- vref+ +4.096 voltage reference (note 1) acom ain +2.5 v smode cs 5 sclk 5 sdo rdy conv mclk dither rst bp/up 1. see section 3.3 voltage reference for information on required voltage reference performance criteria. 2.locate capacitors so as to minimize loop length. 3. the 2.5 v supplies should also be bypassed to ground at the converter. 4. vlr and the power supply ground for the 2.5 v should be connected to the same ground plane under the chip. 5. sclk and sdo may require pull-down resistors in some applications. notes -2.5 v bufen (v-) buffers off (v+) buffers on 10 f0.1 f v1+ v2+ v1- v2- vl vlr dcr +2.5 v +3.3 v to +1.8 v 0.1 f 0.1 f x7r 0.1 f 10 49.9 150pf 2k 4700pf c0g -2.048 v +2.048 v 0 v -2.5 v cs5571 tst 10 0.1 f 50 vlr2
cs5571 18 ds768pp1 3/25/08 10:56 the following figure depicts the cs5571 part power ed from a single 5v analog supply and configured for unipolar measurement. figure 7. cs5571 configured for unipolar measurement using a single 5v analog supply acom ain smode cs 4 sclk 4 sdo rdy conv bp/up mclk dither rst tst vref- vref+ +4.096 voltage reference (note 1) +5 v bufen 1. see section 3.3 voltage reference for information on required voltage reference performance criteria. 2. locate capacitors so as to minimize loop length. 3. v1-, v2-, and vlr should be connected to the same ground plane under the chip. 4. sclk and sdo may require pull-down resistors in some applications. notes 0.1 f (v-) buffers off (v+) buffers on 0.1 f 10 f v1+ v2+ v1- v2- vl vlr dcr +5 v +3.3 v to 1.8 v 0.1 f 0.1 f x7r 0.1 f 10 49.9 150pf 2k 4700pf c0g 0 v to +2.048 v cs5571 50 vlr2 cs3003 / cs3004
cs5571 ds768pp1 19 3/25/08 10:56 the following figure depicts the cs5571 part power ed from a single 5v analog supply and configured for bipolar measurement, referenced to a common mode voltage of 2.5 v. figure 8. cs5571 configured for bipolar measurement using a single 5v analog supply acom ain smode cs 4 sclk 4 sdo rdy conv cal bp/up mclk dither rst tst vref- vref+ +4.096 voltage reference (note 1) +5 v bufen 1. see section 3.3 voltage reference for information on required voltage reference performance criteria. 2. locate capacitors so as to minimize loop length. 3. v1-, v2-, and vlr should be connected to the same ground plane under the chip. 4. sclk and sdo may require pull-down resistors in some applications. notes 0.1 f (v-) buffers off (v+) buffers on 0.1 f 10 f v1+ v2+ v1- v2- vl vlr dcr +5 v +3.3 v to 1.8 v 0.1 f 0.1 f x7r 0.1 f 10 49.9 150pf 2k 4700pf c0g cs5571 49.9 150pf 2k 4700pf c0g common mode voltage (2.5 v typ.) +0.452 v +4.548 v +2.5 v vlr2 50 cs3003 / cs3004 cs3003 / cs3004
cs5571 20 ds768pp1 3/25/08 10:56 3.7 ain & vref sampling structures the cs5571 uses on-chip buffers on the ain and vref + inputs. buffers provide much higher input im- pedance and therefore reduce the amount of drive cu rrent required from an external source. this helps minimize errors. the buffer enable (bufen) pin determines if the on-ch ip buffers are used or not. if the bufen pin is connected to the v1+ supply, the buffers will be enabled . if the bufen pin is connected to the v1- pin, the buffers are off. the converter will consume about 30 mw less power when the buffers are off, but the input impedances of ain, acom and vref+ will be significantly less than with the buffers enabled. 3.8 converter performance the cs5571 achieves excellent differential nonlinearity (dnl) as shown in figures 9 and 10. figure 9 il- lustrates the code widths on a typical scale of 1 lsb. figure 10 illustrates a zoom view of figure 9 on a scale of 0.1 lsb. figure 10 also includes a dnl error histogram that indicates that the errors are equally distributed about the perfect code size; and mo st codes are accurate within 0.01 lsb. figure 9. cs5571 dnl plot figure 10. cs5581 dnl error plot with dnl histogram -1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 1 65535 dnl error in lsbs codes 2k 4k 6k 8k 10k 12k 14k 16k 18k 0 0 +0.08 +0.07 +0.06 +0.05 +0.04 +0.03 +0.02 +0.01 -0.01 -0.02 -0.03 -0.04 -0.05 -0.06 -0.07 -0.08 -0.09 -0.1 +0.09 +0.1 dnl error in lsbs counts per 0.01 lsb error -0.10 -0.08 -0.06 -0.04 -0.02 0 +0.02 +0.04 +0.06 +0.08 +0.10 1 65535 codes dnl error in lsbs
cs5571 ds768pp1 21 3/25/08 10:56 figures 11, 12, and 13 indicate t he spectral performance of the cs5571 with a 0 db, -6 db and - 12 db 5.55 khz input signal. in each case, the captured data was windowed with a seven-term window function that exhibits 4.3 db of attenuation before being processed by the fft. -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) 5.55 khz, -12 db 32k samples @ 100 ksps -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) 5.55 khz, -6 db 32k samples @ 100 ksps -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) 5.55 khz, 0 db 32k samples @ 100 ksps figure 11. spectral performance, 0 db figure 12. spectral performance, -6 db figure 13. spectral performance, -12 db
cs5571 22 ds768pp1 3/25/08 10:56 figures 14 and 15 illustrate the small signal perfo rmance of the cs5571 with a 5.55 khz signal at -80 db down. figure 14 is with dither on and figure 15 is with dither off. at -80 db the signal is 1/10,000 of full scale, having a peak-to-pea k magnitude of only a few codes. for small signals, dnl errors and quantization errors can introduce distortion because the error in the code size, or the quantization error without adequate dither, are a much greater percentage of the signal than with a full-scale input. figure 15, with dither off, illustrates that distortion components can be introduced when there is not adequate dither to randomize the quantization error. figures 16 and 17 illustrate dither on and dither off with a 5.55 khz input at -100 db. at -100 db the signal is only about 41 microvolts peak to peak. this is less than the one code width which is about 62.5 microvolts. -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) 5.55 khz, -80 db 32k samples @ 100 ksps dither on figure 14. spectral performance, -80 db dither on figure 15. spectral performance, -80 db dither off -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) figure 16. spectral performance, -100 db dither on figure 17. spectral performance, -100 db dither off
cs5571 ds768pp1 23 3/25/08 10:56 figure 18 illustrates a test signal of 5.55 khz, 11 6.3 db down, which is only 6.3 microvolts peak to peak, or about 1/10 of a code width. the converter can reliably digitize this signal because of its excellent dnl and proper dither. figure 19 is a spectral plot of the converter with it s input grounded. the spectral information is on a log- arithmic frequency axis as this illustrates the very low frequency behavior of the converter. figure 19 was produced from averaging the results of 16 fft outputs using 2 million samples each . this plot also illus- trates that the converter noise floor is free of s purious components that may be present in other converters due to on-chip digital interference. -160 -140 -120 -100 -80 -60 -40 -20 0 0 10k 20k 30k 40k 50 k frequency (hz) figure 18. spectral performance, -116.3 db dither on -140 -120 -100 -80 0.1 1 10 100 1k 10k -160 -180 -60 -40 -20 0 50 k frequency (hz) shorted input 2m samples @ 100 ksps 16 averages figure 19. spectral plot of noise with shorted input
cs5571 24 ds768pp1 3/25/08 10:56 figure 20 illustrates a noise histogram of 4096 sample s with the input signal adjusted to almost the exact center of a code with dither on. figure 21 illustrates a noise histogram of 4096 samples with the input signal at the center of a code with dither off. notice that with a signal at the center of a code that the converter outputs the same code over 96% of the time. figures 22 and 23 illustrate the noise histogram, dither on and then dither off with the input signal at a code boundary. notice that in the dith er off case the converter only exhibits two codes of noise. 3.9 dither from the performance plots, one should conclude that the best ac performanc e for small signals occurs with dither on. for capturing multiple samples and performing averaging, dith er should also be on because the dither will randomize the quantization noise of the converter and provide improved accuracy. however, if only one conversion is to be taken on a dc input, dither should be set to off. with dither off, the converter exhibits only two codes of noise if the signal is at any point other than the exact center of a code. this means that with dither off the co nverter will nominally yi eld over 32,000 noise-free counts. output (codes) 3 2624 9 0 500 1000 1500 2000 2500 3000 3500 4000 4500 -2 -1 0 output (codes) 12 751 709 0 500 1000 1500 2000 2500 3000 3500 4000 4500 75 3940 81 00 -2 -1 0 output (codes) 12 figure 20. noise histogram, 4096 samples dither on, code center figure 21. noise histogram, 4096 samples dither off, code center 58 0 1953 66 2019 0 500 1000 1500 2000 2500 3000 3500 4000 4500 -2 -1 0 output (codes) 12 output (codes) 2050 2046 -2 -1 0 1 2 0 500 1000 1500 2000 2500 3000 3500 4000 4500 00 0 figure 22. noise histogram, 4096 samples dither on, input at code boundary figure 23. noise histogram, 4096 samples dither off, input at code boundary
cs5571 ds768pp1 25 3/25/08 10:56 3.10 digital filt er characteristics the digital filter is designed for fast settling, therefor e it exhibits very little in-band attenuation. the filter attenuation is 1.040 db at 50 khz when sampling at 100 ksps. figure 24. cs5571 digital filter response (dc to fs/2) figure 25. cs5571 digital filter response (dc to 10 khz) figure 26. cs5571 digital filter response (dc to 4fs) -1.50 -1.25 -1.00 -0.75 -0.50 -0.25 0.00 0 10k 20k 30k 40k 50k frequency (hz) -0.0414 db -0.1660 db -0.3740 db -0.6660 db -1.040 db fs = 100 ksps -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0 2k4k6k8k10k frequency (hz) -0.001650 db -0.00700 db -0.01490 db -0.02643 db -0.04140 db fs = 100 ksps -120 -100 -80 -60 -40 -20 0 0 100k 200k 300k 400k frequency (hz) fs = 100 ksps
cs5571 26 ds768pp1 3/25/08 10:56 3.11 serial port the serial port on the cs5571 can operate in two different modes: synchronous self clock (ssc) mode & synchronous external clock (sec) mode. the serial por t must be placed into the sec mode if the offset and gain registers of the converter are to be read or written. the converter must be idle when reading or writing to the on-chip registers. 3.11.1 ssc mode if the smode pin is high (smode = vl), the serial port operates in the ssc (synchronous self clock) mode. in the ssc mode the port shi fts out conversion data words with sclk as an output. sclk is gen- erated inside the converter from mclk. data is output from the sdo (serial data output) pin. if cs is high, the sdo and sclk pins will stay in a high-impedance state. if cs is low when rdy falls, the con- version data word will be output from sdo msb first. da ta is output on the rising edge of sclk and should be latched into the external logic on the subsequent rising edge of sclk. when all bits of the conversion word are output from the port the rdy signal will return to high. 3.11.2 sec mode if the smode pin is low (smode = vlr), the serial port operates in the sec (synchronous external clock mode). in this mode, the user usually monitors rdy . when rdy falls at the end of a conversion, the conversion data word is placed into the output data register in the serial port. cs is then activated low to enable data output. note that cs can be held low continuously if it is not necessary to have the sdo output operate in the high impedance state. when cs is taken low (after rdy falls) the conversion data word is then shifted out of the sdo pin by driving the sclk pin from system logic external to the converter. data bits are advanced on rising edges of sclk and latched by the subsequent rising edge of sclk. if cs is held low continuously, the rdy signal will fall at the end of a conversion and the conversion data will be placed into the serial port. if the user starts a read, the user will maintain control over the serial port until the port is empty. however, if sclk is not toggled, the converter will overwrite the conversion data at the completion of the next conversion. if cs is held low and no read is performed, rdy will rise just prior to the end of the next conversion and then fall to signal that new data has been written into the serial port. 3.12 power supplies & grounding the cs5571 can be configured to operate with its anal og supply operating from 5v, or with its analog sup- plies operating from 2.5v. the digital interface supports digital logic operating from either 1.8v, 2.5v, or 3.3v. figure 6 on page 17 illustrates the device configured to operate from 2.5v analog. figure 7 on page 18 illustrates the device configured to operate from 5v analog. to maximize converter performance, the analog groun d and the logic ground for the converter should be connected at the converter. in the dual analog supply configuration, the analog ground for the 2.5v sup- plies should be connected to the vlr pin at the conver ter with the converter placed entirely over the an- alog ground plane. in the single analog supply configuration (+5v), the ground for the +5v supply should be directly tied to the vlr pin of the converter with the converter pl aced entirely over the analog ground plane. refer to figure 7 on page 18.
cs5571 ds768pp1 27 3/25/08 10:56 3.13 using the cs5571 in mu ltiplexing applications the cs5571 is a delta-sigma a/d converter. delta- sigma converters use oversampling as means to achieve high signal-to-noise performance. this means that once a conversion is started, the converter takes many samples to compute the resulting output word. the analog input for the signal to be converted must remain active during the entire conversion until rdy falls. the cs5571 can be used in multiplexing applications , but the system timing for changing the multiplexer channel and for starting a new conversion will depend upon the multiplexer system architecture. the simplest system is illustrated in figure 27 . any time the multiplexer is changed, the analog signal presented to the converter must fully settle. after the signal has settled, the conv signal is issued to the converter to start a conversion. being a delta-sigma c onverter, the signal must remain present at the input of the converter until the conversion is comple ted. once the conversion is completed, rdy falls. at this time the multiplexer can be changed to the next channel and the data can be read from the serial port. the conv signal should be delayed until after the data is read and until the new analog signal has settled. in this configuration, the throughput of the converter will be dictated by the settling time of the analog input circuit and the conversion time of the converter. the conversion data can be read from the serial port after the multiplexer is changed to the new channel while the analog input signal is settling. figure 27. simple multiplexing scheme a more complex multiplexing scheme can be used to incr ease the throughput of the converter is illustrated in figure 28 . in this circuit, two banks of multiplexers are used. amplifier settling time conversion time amplifier settling time ch1 ch2 conv rdy advance mux throughput cs5571 ain acom ch1 ch2 ch3 ch4 90 150pf 2k 4700pf c0g
cs5571 28 ds768pp1 3/25/08 10:56 at the same time the converter is performing a conv ersion on a channel from one bank of multiplexers, the second multiplexer bank is used to select the ch annel for the next conversion. this configuration al- lows the buffer amplifier for the second multiplexer bank to fully settle while a conversion is being per- formed on the channel from the first multiplexer bank. the multiplexer on the output of the buffer amplifier and the conv signal can be changed at the same time in this configuration. this multiplexing architec- ture allows for maximum multiplexing throughput from the a/d converter. the following figure depicts the recommended analog input amplifier circuit. figure 28. more complex multiplexing scheme conv convert on ch1 convert on ch1 convert on ch4 convert on ch3 convert on ch2 select a1 select a2 select a1 select a2 select ch1 select ch3 select ch1 select a1 select ch2 select ch4 select ch2 sw1 sw2 sw3 cs5571 ain acom 90 150pf 2k 4700pf c0g 90 150pf 2k ch1 ch3 ch2 ch4 sw2 sw3 sw1 a2 a1 4700pf c0g
cs5571 ds768pp1 29 3/25/08 10:56 3.14 synchronizing multiple converters many measurement systems have multiple converte rs that need to operate synchronously. the convert- ers should all be driven from the same master clock. in this configuration, the converters will convert syn- chronously if the same conv signal is used to drive all the converters, and conv falls on a falling edge of mclk. if conv is held low continuously, reset (rst ) can be used to synchronize multiple converters if rst is released on a falling edge of mclk.
cs5571 30 ds768pp1 3/26/08 14:22 4. pin descriptions cs ? chip select, pin 1 the chip select pin allows an external device to access the serial port. when held high, the sdo output will be held in a high-impedance output state. tst ? factory test, pin 2 for factory use only. connect to vlr. smode ? serial m ode select, pin 3 the serial interface mode pin (smode) dictates wh ether the serial port behaves as a master or slave interface. if smode is tied high (to vl ), the port will operat e in the synchronous self-clocking (ssc) mode. in ssc mode, the port ac ts as a master in which the converter out- puts both the sdo and sclk signals. if smode is tied low (to vlr), the port will operate in the synchronous external clocking (sec) mode. in se c mode, the port acts as a slave in which the external logic or microcontroller generates the sclk used to output the conversion data word from the sdo pin. ain ? analog input, pin 4 ain is the single-ended input. acom ? analog return, pin 5 acom is the analog return for the input signal. v1- ? negative power 1, pin 6 the v1- and v2- pins provide a negative supply vo ltage to the core circuitry of the chip. these two pins should be decoupled as shown in t he application block diagrams. v1- and v2- should be supplied from the same source voltage. for si ngle-supply operation, these two voltages are nominally 0 v (ground). for dual-supply operation, they are nominally -2.5 v. v1+ ? positive power 1, pin 7 the v1+ and v2+ pins provide a positive supply vo ltage to the core circui try of the chip. these two pins should be decoupled as shown in the application block diagrams. v1+ and v2+ should be supplied from the same source voltage. for si ngle supply-operation, these two voltages are nominally +5 v. for dual-supply oper ation, they are nominally +2.5 v. bufen ? buffer enable, pin 8 buffers on input pins ain and acom are enabled if bufen is connected to v1+ and disabled if connected to v1-. vref+, vref- ? voltage reference input, pins 9, 10 a differential voltage reference input on these pins functions as the vo ltage reference for the converter. the voltage between these pins can range between 2.4 volts and 4.2 volts, with 4.096 volts being the nominal reference voltage value. rst reset vlr2 logic interface return conv convert dcr digital core regulator v2+ positive voltage 2 v2- negative voltage 2 mclk master clock vlr logic interface return vl logic interface power sdo serial data output sclk serial clock input/output rdy ready dither dither select bp/up bipolar/unipolar select vref- voltage reference input vref+ voltage reference input bufen buffer enable v1+ positive power 1 v1- negative power 1 acom analog return ain analog input cs chip select tst factory test smode serial mode select 12 11 10 9 8 7 6 5 4 3 2 1 13 14 15 16 17 18 19 20 21 22 23 24
cs5571 ds768pp1 31 3/25/08 10:56 bp/up ? bipolar/unipolar select, pin 11 the bp/up pin determines the span and the output c oding of the converter. when set high to select bp (bipolar), the input span of the converter is -2.048 volts to +2.048 volts (assuming the voltage reference is 4.096 volts) and output data is coded in two's complement format. when set low to select up (unipolar), the input span is 0 to +2.048 and the output data is coded in binary format. dither ? dither select, pin 12 when dither is high (dither = vl ), output conversion words w ill be dithered. when dither is low (dither = vlr), ou tput words will be domi nated by quantization. rst ? reset, pin 13 reset is necessary after powe r is initially applied to th e converter. when the rst input is taken low, the logic in the converter will be reset. when rst is released to go high, certain portions of the analog circuitry are started. rdy falls when rese t is complete. conv ? convert, pin 15 the conv pin initiates a conversion cycle if taken lo w, a previous conversion is in progress. when the conversion cycle is completed, the conversi on word is output to th e serial port register and the rdy signal goes low. if conv is held low and remains low when rdy falls, another conversion cycle will be started. dcr ? digital core regulator, pin 16 dcr is the output of the on-chip regulator for the digital logic core. dcr should be bypassed with a capacitor to v2-. the dcr pin is not designed to power any external load. v2+ ? positive power 2, pin 17 the v1+ and v2+ pins provide a positive supply voltage to the circuitry of the chip. these two pins should be decoupled as shown in the application block diagrams. v1+ and v2+ should be supplied from the same source voltage. for si ngle-supply operation, these two voltages are nominally +5 v. for dual-supply oper ation, they are nominally +2.5 v. v2- ? negative power 2, pin 18 the v1- and v2- pins provide a negative supply vo ltage to the circuitry of the chip. these two pins should be decoupled as shown in the app lication block diagrams. v1- and v2- should be supplied from the same source voltage. for si ngle-supply operation, these two voltages are nominally 0 v (ground). for dual-supply operation, they are nominally -2.5 v. mclk ? master clock, pin 19 the master clock pin (mclk) is a multi-function pin. if tied low (mclk = vlr), the on-chip oscil- lator will be enabled. if tied high (mclk = vl), a ll clocks to the internal ci rcuitry of th e converter will stop. when mclk is held hi gh the internal oscillator will al so be stopped. mclk can also function as the input for an external cmos-compa tible clock that conforms to supply voltages on the vl and vlr pins. vlr2, vlr, vl ? logic interface power/return, pins 14, 20, 21 vl and vlr are the supply voltages for the digital logic interface. vl and vlr can be config- ured with a wide range of common mode voltage. the following interface pins function from the vl/vlr supply: smode, cs , sclk, tst, sdo, rdy , dither, conv , rst , bp/up , and mclk. sdo ? serial data output, pin 22 sdo is the output pin for the seri al output port. data from this pin will be output at a rate deter- mined by sclk and in a format determined by the bp/up pin. data is output msb first and advances to the next data bit on the rising edges of sclk. sdo will be in a high impedance state when cs is high.
cs5571 32 ds768pp1 3/25/08 10:56 sclk ? serial clock input/output, pin 23 the smode pin determines whether the sclk signal is an input or an output signal. sclk determines the rate at which data is clocked ou t of the sdo pin. if the converter is in ssc mode, the sclk frequency will be determined by the master clo ck frequency of the converter (either mclk or the internal os cillator). in sec mode, the user determines the sclk frequency. if sclk is an output (smode = vl), it w ill be in a high-impedance state when cs is high. rdy ? ready, pin 24 if conv is low the converter will immedi ately start a conversion and rdy will remain high until the conversion is completed. at the end of any conversion rdy falls to indicate that a conver- sion word has been placed into the serial port. rdy will return high after a ll data bits are shifted out of the serial port or two master clock cycles before new data becomes available if the cs pin is inactive (high); or two mast er clock cycles before new data becomes available if the user holds cs low but has not started reading the data from the converter when in sec mode.
cs5571 ds768pp1 33 3/25/08 10:56 5. package dimensions notes: 1.?d? and ?e1? are reference datums and do not included mold flas h or protrusions, but do include mold mismatch and are measure d at the parting line, mold flash or prot rusions shall not exceed 0.20 mm per side. 2.dimension ?b? does not include dambar prot rusion/intrusion. allowable dambar protru sion shall be 0.13 mm total in excess of ?b ? dimension at maximum material condition. dambar intrusion shall not reduce dimens ion ?b? by more than 0.07 mm at least material condition. 3.these dimensions apply to the flat section of the lead between 0.10 and 0.25 mm from lead tips. inches millimeters note dim min nom max min nom max a -- -- 0.084 -- -- 2.13 a1 0.002 0.006 0.010 0.05 0.13 0.25 a2 0.064 0.068 0.074 1.62 1.73 1.88 b 0.009 -- 0.015 0.22 -- 0.38 2,3 d 0.311 0.323 0.335 7.90 8.20 8.50 1 e 0.291 0.307 0.323 7.40 7.80 8.20 e1 0.197 0.209 0.220 5.00 5.30 5.60 1 e 0.022 0.026 0.030 0.55 0.65 0.75 l 0.025 0.03 0.041 0.63 0.75 1.03 0 4 8 0 4 8 jedec #: mo-150 controlling dimension is millimeters. 24l ssop package drawing e n 1 23 e b 2 a1 a2 a d seating plane e1 1 l side view end view top view
cs5571 34 ds768pp1 3/25/08 10:56 6. ordering information 7. environmental, manufact uring, & handlin g information * msl (moisture sensitivity level) as specified by ipc/jedec j-std-020. 8. revision history model linearity temperature conversion time throughput package CS5571-ISZ .0008% -40 to +85 c 10 s 100 ksps 24-pin ssop model number peak reflow temp msl rating* max floor life CS5571-ISZ 260 c 3 7 days revision date changes pp1 mar 2008 preliminary release. contacting cirrus logic support for all product questions and inquiries cont act a cirrus logic sales representative. to find the one nearest to you go to www.cirrus.com important notice "preliminary" product information describes products that are in production, but for which full characterization data is not ye t available. cirrus logic, inc. and its subsidiaries ("cirrus") believe that the information contained in this document is accurate and reli able. however, the information is subject to change without notice and is provided "as is" without warranty of any kind (express or implied). customers are advised to ob tain the latest version of relevant information to verify, before placing orders, that information be ing relied on is current and complete. all products are sold s ubject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liabil ity. no responsibility is assumed by cirrus for the use of this information, including use of this informatio n as the basis for manufacture or sale of any items, or for in fringement of patents or other rights of third parties. this document is the property of cirrus and by furnishing this information, cirrus grants no license, express or impli ed under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual property rights. cirrus owns the copyrights associated with the inf ormation contained herein and gives con- sent for copies to be made of the information only for use within your organization with respect to cirrus integrated circuits or other products of cirrus. this consent does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale. certain applications using semiconductor products may involve po tential risks of deat h, personal injury, or severe prop- erty or environmental damage ("critical applications"). cirrus products are not de signed, authorized or warranted for use in products surgically implanted into the body, automotive safety or sec urity devices, life support products or other crit- ical applications. inclusion of cirrus prod ucts in such applications is understood to be fully at the customer's risk and cir- rus disclaims and makes no warra nty, express, statutory or impl ied, including the implied wa rranties of merchantability and fitness for particular purpose, with rega rd to any cirrus product that is used in such a manner. if the customer or custom- er's customer uses or permits the use of cirrus products in critical applications , customer agre es, by such use, to fully indemnify cirrus, its officers, directors, employees, distributors and other agents from any and all liability, including at- torneys' fees and costs, that may result from or arise in connection with these uses. cirrus logic, cirrus, and the cirrus logic logo designs are trade marks of cirrus logic, inc. all other brand and product names in this document may be trademarks or service marks of their respective owners.

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