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1 12-bit, 1msps sar adcs ISL267450 the ISL267450 is a 12-bit, 1msps sampling sar-type adc with a differential input span of 2*v ref volts. the ISL267450 features excellent linearity over supply an d temperature variations and is drop-in compatible with the ad7450. the device can operate from a supply voltage of either 5v or 3v and maintain measurement accuracy with input signals up to the supply rails. the serial digital interface is spi compatible and is easily interfaced to popular fpgas and microcontrollers. power dissipation is 9.0mw at a sampling rate of 1msps, and just 5w between conversions utilizing auto power-down mode (with a 3v supply). the ISL267450 is available in 8 ld soic or msop packages, and are specified for operation over the industrial temperature range (?40c to +85c). features ? drop-in compatible with ad7450 ? differential input ? simple spi-compatible serial digital interface ? guaranteed no missing codes ? 1mhz sampling rate ? 3v or 5v operation ?low operating current - 1.25ma at 833ksps with 3v supplies - 1.7ma at 1msps with 5v supplies ? power-down current between conversions: 1a ? excellent differential non-linearity ? low thd: -83db (typ) ? pb-free (rohs compliant) ? available in soic and msop packages applications ? remote data acquisition ? battery operated systems ? industrial process control ? energy measurement ? data acquisition systems ? pressure sensors ? flow controllers block diagram adc serial interface +v dd v ref gnd v in+ v in- sclk sdata cs august 10, 2012 fn8341.0 caution: these devices are sensitive to electrostatic discharge; follow proper ic handling procedures. 1-888-intersil or 1-888-468-3774 | copyright intersil americas inc. 2012. all rights reserved intersil (and design) is a trademark owned by intersil corporation or one of its subsidiaries. all other trademarks mentioned are the property of their respective owners.
ISL267450 2 fn8341.0 august 10, 2012 typical connection diagram v ref v in+ v in? gnd v dd sclk sdata cs v ref(p-p) + +3v/5v supply p/c v ref serial interface 10f 0.1f v ref(p-p) 0.1f pin configuration ISL267450 (8 ld soic, msop) top view v ref v dd gnd cs v in- sdata v in+ sclk 1 2 3 4 8 7 6 5 pin description ISL267450 description pin name pin number v dd 8 supply voltage, +2.7v to 5.25v. sclk 7 serial clock input. controls digital i/o timing and clocks the conversion. sdata 6 digital conversion output. cs 5 chip select input. controls the star t of a conversion when going low. gnd 4 ground v in? 3 negative analog input. v in+ 2 positive analog input. v ref 1 reference voltage.
ISL267450 3 fn8341.0 august 10, 2012 ordering information part number (notes 1, 2, 3) part marking vdd range (v) temp range (c) package (pb-free) pkg. dwg. # ISL267450ibz 267450 ibz 2.7 to 5.25 -40 to +85 8 ld soic m8.15 ISL267450iuz 67450 2.7 to 5.25 -40 to +85 8 ld msop m8.118 notes: 1. add ?-t*? suffix for tape and reel. please refer to tb347 for details on reel specifications. 2. these intersil pb-free plastic packaged products employ spec ial pb-free material sets, molding compounds/die attach materials , and 100% matte tin plate plus anneal (e3 termination finish , which is rohs compliant and compatible wi th both snpb and pb-free soldering opera tions). intersil pb-free products are msl classified at pb-fr ee peak reflow temperatures that meet or exceed the pb-free requirements of ipc/jed ec j std-020. 3. for moisture sensitivity level (msl), please see device information page for ISL267450 . for more information on msl please see techbrief tb363 .
ISL267450 4 fn8341.0 august 10, 2012 table of contents absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 thermal information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 typical performance characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 adc transfer function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 analog input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 voltage reference input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 converter operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 acquisition time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 short cycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 power vs throughput rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 grounding and layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 signal-to-(noise + distortion) ratio (sinad) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 total harmonic distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 peak harmonic or spurious noise (sfdr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 intermodulation distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 aperture delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 aperture jitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 full power bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 common-mode rejection ratio (cmrr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 integral nonlinearity (inl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 differential nonlinearity (dnl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 zero-code error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 positive gain error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 negative gain error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 track and hold acquisition time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 power supply rejection ratio (psrr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 package outline drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 package outline drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
ISL267450 5 fn8341.0 august 10, 2012 absolute maximum rating s thermal information any pin to gnd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to +6.0v analog input to gnd. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to v dd +0.3v digital i/o to gnd. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to v dd +0.3v digital input voltage to gnd . . . . . . . . . . . . . . . . . . . . . . . -0.3v to v dd +0.3v maximum current in to any pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10ma esd rating human body model (tested per jesd22-a114f) . . . . . . . . . . . . . . . . 8kv machine model (tested per jesd22-a115b) . . . . . . . . . . . . . . . . . 400v charged device model (tested per jesd22-c101e). . . . . . . . . . . . 1.5kv latch up (tested per jesd78c; class 2, level a) . . . . . . . . . . . . . . . 100ma thermal resistance (typical) ja (c/w) jc (c/w) 8 ld soic package (notes 4, 5). . . . . . . . . . 120 64 8 ld msop package (notes 4, 5). . . . . . . . . 165 64 operating temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40c to +85c storage temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-65c to +150c junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+150c pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see link below http://www.intersil.com/ pbfree/pb-freereflow.asp caution: do not operate at or near the maximum ratings listed for extended periods of time. exposure to such conditions may adv ersely impact product reliability and result in failures not covered by warranty. notes: 4. ja is measured with the component mounted on a high effective thermal conductivity test board in free air. see tech brief tb379 for details. 5. for jc , the ?case temp? location is taken at the package top center. electrical specifications v dd = +3.0v to +3.3v, f sclk = 15mhz, f s = 833ksps, v ref = 1.25v, f in = 200khz; v dd = +4.75v to +5.25v, f sclk = 18mhz, f s =1msps, v ref = 2.5v, f in = 300khz; v cm = v ref , t a = t min to t max unless otherwise noted. typical values are at t a = +25c. boldface limits apply over the operating temperature range, -40c to +85c. symbol parameter test conditions min (note 6) typ max (note 6) units dynamic performance sinad signal-to (noise + distortion) ratio v dd = 5v 70 db v dd = 3v 67 db thd total harmonic distortion v dd = 5v -80 -75 db v dd = 3v -78 -73 db sfdr spurious free dynamic range v dd = 5v -82 -75 db v dd = 3v -80 -73 db imd intermodulation distortion 2nd order terms ?89 db 3rd order terms -85 db tpd aperture delay 10 ns tpd aperture jitter 50 ps 3db full power bandwidth @ ?3db 20 mhz @ ?0.1db 2.5 mhz psrr power supply rejection ratio -87 db dc accuracy nresolution 12 bits inl integral nonlinearity -1 1 lsb dnl differential nonlinearity guaranteed no missed codes to 12 bits -0.95 0.95 lsb offset zero-code error v dd = 5v -3 3 lsb v dd = 3v -6 6 lsb gain positive gain error v dd = 5v -3 3 lsb v dd = 3v -6 6 lsb negative gain error v dd = 5v -3 3 lsb v dd = 3v -6 6 lsb
ISL267450 6 fn8341.0 august 10, 2012 analog input (note 7) |ain| full-scale input span 2 x v ref v in+ - v in? v v in+ , v in? absolute input voltage range v cm = v ref v v in+ v cm v ref /2 v vin? v cm v ref /2 v i leak input leakage current -1 1 a c vin input capacitance track mode 12 pf hold mode 6 pf reference input v ref v ref input voltage range v dd = 5v (1% tolerance for specified performance) 2.5 v v dd = 3v (1% tolerance for specified performance) 1.25 v i leak dc leakage current -1 1 a c vref v ref input capacitance 19 pf logic inputs v ih input high voltage 2.4 v v il input low voltage 0.8 v i leak input leakage current -1 1 a c in input capacitance 10 pf logic outputs v oh output high voltage i source = 200a v dd - 0.3 v v ol output low voltage i sink = 200a 0.4 v i leak floating-state leakage current -1 1 a c out floating-state output capacitance 10 pf output coding two?s complement conversion rate t conv conversion time 888ns with f sclk = 18mhz 16 sclk cycles 1.07s with f sclk = 15mhz 16 sclk cycles t acq acquisition time (note 8) sine wave input 200 ns f max throughput rate v dd = 5v 1 msps v dd = 3v 833 ksps power requirements v dd positive supply voltage range 3.3v 10% 3.0 3.6 v 5v 5% 4.75 5.25 v electrical specifications v dd = +3.0v to +3.3v, f sclk = 15mhz, f s = 833ksps, v ref = 1.25v, f in = 200khz; v dd = +4.75v to +5.25v, f sclk = 18mhz, f s =1msps, v ref = 2.5v, f in = 300khz; v cm = v ref , t a = t min to t max unless otherwise noted. typical values are at t a = +25c. boldface limits apply over the operating temp erature range, -40c to +85c. (continued) symbol parameter test conditions min (note 6) typ max (note 6) units
ISL267450 7 fn8341.0 august 10, 2012 i dd positive supply input current static v dd = 3v/5v; sclk on or off 1 a dynamic v dd = 5v; f s = 1msps 1.7 ma v dd = 3v; f s = 833ksps 1.25 ma p d power dissipation static mode v dd = 3v/5v; sclk on or off 5 w dynamic v dd = 5v; f s = 1msps 8.5 mw v dd = 3v; f s = 833ksps 3.75 mw notes: 6. compliance to datasheet limits is assu red by one or more methods: production test, characterization and/or design. 7. the absolute voltage applied to each analog input must not exceed v dd . 8. read about ?acquisition time? on page 14 for a discussion of this parameter. electrical specifications v dd = +3.0v to +3.3v, f sclk = 15mhz, f s = 833ksps, v ref = 1.25v, f in = 200khz; v dd = +4.75v to +5.25v, f sclk = 18mhz, f s =1msps, v ref = 2.5v, f in = 300khz; v cm = v ref , t a = t min to t max unless otherwise noted. typical values are at t a = +25c. boldface limits apply over the operating temp erature range, -40c to +85c. (continued) symbol parameter test conditions min (note 6) typ max (note 6) units electrical specifications limits established by characterizati on and are not production tested. v dd = +4.75v to +5.25v, f sclk = 18mhz, f s =1msps, v ref = 2.5v, f in = 300khz; v cm = v ref , t a = t min to t max unless otherwise noted. typical values are at t a = +25c. boldface limits apply over the operating temperature range, -40c to +85c. symbol parameter test conditions min (note 6) typ max (note 6) units fsclk clock frequency 0.05 18 mhz t sclk clock period 55 ns t convert conversion time 16 x t sclk 888 ns t quiet quiet time before sample 25 ns t css cs falling edge to s clk falling edge setup time 10 ns t disable cs falling edge to sdata disable time (note 9) extrapolated back to true bus relinquish 10 35 ns data access time after sclk falling edge t swh sclk high pulsewidth 0.4 x t sclk 0.6 x t sclk ns t swl sclk low pulsewidth 0.4 x t sclk 0.6 x t sclk ns t clkdv sclk falling edge to sdata valid 40 ns t sdh sclk falling edge to sdata hold 10 ns t acq acquisition time (note 8) ns t csw cs pulse width 10 ns t cdv cs falling edge to sdata valid 20 ns electrical specifications limits established by characterizati on and are not production tested. v dd = +3.0v to +3.3v, f sclk = 15mhz, f s = 833ksps, v ref = 1.25v, f in = 200khz; v ref = 2.5v; v cm = v ref , t a = t min to t max unless otherwise noted. typical values are at t a = +25c. boldface limits apply over the operating temperature range, -40c to +85c. symbol parameter test conditions min (note 6) typ max (note 6) units fsclk clock frequency 0.05 15 mhz t sclk clock period 55 ns t convert conversion time 16 x t sclk 1.07 s
ISL267450 8 fn8341.0 august 10, 2012 t quiet quiet time before sample 25 ns t css cs falling edge to s clk falling edge setup time 10 ns t disable cs falling edge to sdata disable time (note 9) extrapolated back to true bus relinquish 10 35 s t swh sclk high pulsewidth 0.4 x t sclk 0.6 x t sclk ns t swl sclk low pulsewidth 0.4 x t sclk 0.6 x t sclk ns t clkdv sclk falling edge to sdata valid 40 ns t sdh sclk falling edge to sdata hold 10 ns t acq acquisition time (note 8) ns t csw cs pulse width 10 ns t cdv cs falling edge to sdata valid 20 ns note: 9. during characterization, t disable is measured from the release point with a 10pf load (s ee figure 2 on page 8) and the equivalent timing using the ad7450 loading (50pf) is calculated. electrical specifications limits established by characterizati on and are not production tested. v dd = +3.0v to +3.3v, f sclk = 15mhz, f s = 833ksps, v ref = 1.25v, f in = 200khz; v ref = 2.5v; v cm = v ref , t a = t min to t max unless otherwise noted. typical values are at t a = +25c. boldface limits apply over the operating temperature range, -40c to +85c. (continued) symbol parameter test conditions min (note 6) typ max (note 6) units figure 1. serial interface timing diagram figure 2. equivalent load circuit output pin c l 10 pf v dd 2.85k r l
ISL267450 9 fn8341.0 august 10, 2012 typical performance characteristics figure 3. dynamic perfor mance at 1msps with v dd = 5v figure 4. dynamic performance at 833ksps with v dd = 3v figure 5. sinad vs analog frequency from various supply voltages figure 6. typical dnl for v dd = 5v figure 7. typical dnl for v dd = 3v figure 8. typical inl for v dd = 5v -160 -140 -120 -100 -80 -60 -40 -20 0 0 100 200 300 400 500 frequency (khz) amplitude (dbfs) 8192-point fft f sample = 1msps f in = 300khz sinad = 71.55db thd = -80.88db sfdr = 84.08db -160 -140 -120 -100 -80 -60 -40 -20 0 0 100 200 300 400 frequency (khz) amplitude (dbfs) 8192-point fft f sample = 833ksps f in = 300khz sinad = 69.83db thd = -82.02db sfdr = 82.93db 60 62 64 66 68 70 72 74 10 100 1k test frequency (hz) 2.7v 3.3v 4.75v 5.25v sinad (dbc) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 code dnl (lsb) 0 1024 2048 3072 4096 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 code dnl (lsb) 0 1024 2048 3072 4096 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 code inl (lsb) 0 1024 2048 3072 4096
ISL267450 10 fn8341.0 august 10, 2012 figure 9. typical inl for v dd = 3v figure 10. change in dnl vs v ref for v dd = 5v figure 11. change in dnl vs v ref for v dd = 3.3v figure 12. change in inl vs v ref for v dd = 5v figure 13. change in inl vs v ref for v dd = 3.3v figure 14. change in offset error vs v ref for v dd = 5v and 3.3v typical performance characteristics (continued) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 code inl (lsb) 0 1024 2048 3072 4096 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 v ref (v) dnl (lsb) pos dnl neg dnl 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 v ref (v) dnl (lsb) pos dnl neg dnl 0.00.51.01.52.02.5 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 v ref (v) inl (lsb) pos inl neg inl 0.00.51.01.52.02.53.03.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 v ref (v) inl (lsb) pos inl neg inl 0.00.51.01.52.02.5 -9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 1.0 v ref (v) 3.3v vdd 5v vdd zce (lsb) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
ISL267450 11 fn8341.0 august 10, 2012 functional description the ISL267450 is based on a succ essive approximation register (sar) architecture utilizing capacitive charge redistribution digital-to-analog converters (dacs) . figure 19 shows a simplified representation of the converter. during the acquisition phase (acq), the differential input is stored on the sampling capacitors (cs ). the comparator is in a balanced state since the switch across its inputs is closed. the si gnal is fully acquired after t acq has elapsed, and the switches then transition to the conversion phase (conv) so the stored voltage may be converted to digital format. the comparator will become unbalanced when the differential switch opens and the input switches transition (assuming that the stored voltag e is not exactly at mid-scale). the comparator output reflects whether the stored voltage is above or below mid-scale, which sets the value of the msb. the sar logic then forces the capacitive dacs to adjust up or down by one quarter of full-scale by switching in binarily weighted capacitors. again the comparator output reflects whether the stored voltage is above or below the new value, setting the value of the next lowest bit. this proc ess repeats until all 12 bits have been resolved. figure 15. histogram of the output codes with a dc input for v dd = 5v figure 16. histogram of the ou tput codes with a dc input for v dd = 3v figure 17. change in enob vs v ref for v dd = 5v and 3.3v figure 18. cmrr vs input frequency for v dd = 5v and 3v typical performance characteristics (continued) 0 10000 20000 30000 40000 50000 60000 70000 2044 2045 2046 2047 2048 2049 2050 output code count frequency 0 10000 20000 30000 40000 50000 60000 70000 2044 2045 2046 2047 2048 2049 2050 output code count frequency 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 v ref (v) 3.3v vdd 5v vdd enob (bits) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -110 -100 -90 -80 -70 -60 -50 -40 10 100 1k 10k frequency (khz) psrr (db) figure 19. sar adc architectural block diagram v in+ v in- v ref acq conv acq acq conv conv dac dac sar logic c s c s
ISL267450 12 fn8341.0 august 10, 2012 an external clock must be applied to the sclk pin to generate a conversion result. the allowable frequency range for sclk is 50khz to 18mhz. serial output da ta is transmitted on the falling edge of sclk. the receiving device (fpga, dsp or microcontroller) may latch the data on the rising edge of sclk to maximize set-up and hold times. a stable, low-noise reference voltage must be applied to the v ref pin to set the full-scale input range and common-mode voltage. see ?voltage reference input? on page 13 for more details. adc transfer function the output coding for the isl2 67450 is two?s complement. the first code transition occurs at successive lsb values (i.e., 1 lsb, 2 lsb, and so on). the lsb size of the ISL267450 is 2*v ref /4096. the ideal transfer characteristic of the ISL267450 is shown in figure 20. analog input the ISL267450 features a fully differential input with a nominal full-scale range equal to twice the applied v ref voltage. each input swings v ref v p-p , 180 out-of-phase from one another for a total differential input of 2*v ref (see figure 21). differential signaling offers severa l benefits over a single-ended input, such as: ? doubling of the full-scale input range (and therefore the dynamic range) ? improved even order harmonic distortion ? better noise immunity due to common mode rejection figure 22 shows the relationship between the reference voltage and the full-scale input range for two different values of v ref . note that there is a trade-off between v ref and the allowable common mode input voltage (vcm). the full-scale input range is proportional to v ref ; therefore the vcm range must be limited for larger values of v ref in order to keep the absolute maximum and minimum voltages on the v in+ and v in? pins within specification. figures 23 and 24 illustrate this relationship for 5v and 3v operation, respectively. the dashed lines show the theoretical vcm range based solely on keeping the v in+ and v in? pins within the supply rails. additional rest rictions are imposed due to the required headroom of the input circuitry, resulting in practical limits shown by the shaded area. figure 20. ideal transfer characteristics 1lsb = 2?v ref /4096 100...000 100...001 100...010 111...111 000...000 000...001 011...110 011...111 adc code analog input v in+ ? (v in? ) ? v ref + ?lsb +v ref ? 1?lsb 0v +v ref ? 1lsb figure 21. differential input signaling ISL267450 v cm v ref(p-p) v ref(p-p) v in+ v in- figure 22. relationship between v ref and full-scale range 3.0 5.0 2.0 1.0 4.0 v in+ v in- vcm 2.0v p-p v ref = 2v 3.0 5.0 2.0 1.0 4.0 v in+ v in- vcm 2.5v p-p v ref = 2.5v t v t v
ISL267450 13 fn8341.0 august 10, 2012 voltage reference input the voltage magnitude applied to the v ref pin defines the full scale span of the adc as 2* v ref . the device is specified with a voltage reference of 2.5v for 5v operation and with a voltage reference of 2.0v for 3v operation. but, v ref input accepts voltages ranging from 0.1v to 3.5v for operation from 5 v v dd and voltages ranging from 0.1v to 2.2v for operation from a 3v v dd . figures 25 and 26 illustrate possi ble voltage reference options for the ISL267450. figure 25 uses the isl21090 precision voltage reference, which exhibits exceptionally low drift and low noise. the isl21090 must use a power supply greater than 4.7v. the v ref input pin on the ISL267450 uses very low current, so the decoupling capacitor can be small (0.1f). figure 26 illustrates the isl21010 voltage reference. the isl21010 is available in various output voltages. it has higher noise and drift than the isl 26090, but consumes very low operating current, which makes it an excellent choice for battery-powered applications. figure 23. relationship between v ref and vcm for v dd = 5v 3.0 5.0 2.0 1.0 4.0 v ref vcm 0.5 1.0 1.5 2.0 2.5 3.0 3.5 figure 24. relationship between vref and vcm for v dd = 3v 1.5 2.5 1.0 0.5 2.0 v ref vcm 0.5 1.0 1.5 2.0 2.5 3.0 figure 25. precision voltage reference for +5v supply 1 2 3 4 8 7 6 5 dnc vin comp gnd dnc dnc vout trim 0.1f v dd 0.1f 2.5v v ref 0.1f bulk + 5v isl21090 ISL267450 figure 26. voltage reference for +3.0v to +3.3v, or for +5v supply vdd 0.1f vref 0.1f bulk + +3.0v to +3.3v isl21010 gnd vin vout 1 2 3 0.1f 1.25, 2.048 or 2.5v or +5v ISL267450
ISL267450 14 fn8341.0 august 10, 2012 converter operation the ISL267450 is designed to minimize power consumption by only powering up the sar compar ator during conversion time. when the converter is in track mode (its sample capacitors are tracking the input signal), the sar comparator is powered down. the state of the converter is dictated by the logic state of cs . when cs is high, the sar comparator is powered down while the sampling capacitor array is tracking the input. when cs transitions low, the capacitor array immediately captures the analog signal that is being tracked. after cs is taken low, the sclk pin is toggled 16 times. for the first 3 clocks, the comparator is powered up and auto-zeroed, then the sar decision process is begun. this process uses 12 sclk cycles. each sar decision is presented to the sdata output on the next clock cycle after the sar decision is performed. the sar process (12 bits) is completed on sclk cycle 15. at this point in time, the sar comparator is powered down and the capacitor array is placed back into track mode. th e last sar comparator decision is output from sdata on the 16th sclk cycle. when the last data bit is output from sdata, the outp ut switches to a logic 0 until cs is taken high, at which time, the sdata output enters a high-z state. figure 27 illustrates the serial port system timing for the ISL267450. power-on reset when power is first applied, th e ISL267450 performs a power-on reset that requires approximately 2.5ms to execute. after this is complete, a single dummy conversion must be executed (by taking cs low) in order to initialize the switched capacitor track and hold. the dummy conversion cycle will take 889ns with an 18mhz sclk. once the dummy cycle is complete, the adc mode will be determined by the state of cs . regular conversions can be started immediately after this dummy cycle is completed and time has been allowed for proper acquisition. acquisition time to achieve the maximum sample rate (1msps) in the ISL267450 device, the maximum acquisitio n time is 200ns. for slower conversion rates, or for conversions performed using a slower sclk value than 18mhz, the minimum acquisition time is 200ns. this minimum acquisition time also applies to the device when operated at 3v supply or if short cycling is utilized. short cycling in cases where a lower resolution conversion is acceptable, cs can be pulled high before all 12 bits are clocked out. this is referred to as short cycling, and it can be used to further optimize power dissipation. in this mode, a lower resolution result will be output, but the adc will enter static mode sooner and exhibit a lower average power consumpt ion than if the complete conversion cycle were carried out. the minimum acquisition time (tacq) requirement of 200ns must be met for the next conversion to be valid. power vs throughput rate the ISL267450 provides reduced power consumption at lower conversion rates by automatically switching into a low-power mode after completing a co nversion. the average power consumption of the adc decreases at lower throughput rates. figure 28 shows the typical power consumption over a wide range of throughput rates. figure 27. normal mode operation 0.01 0.1 1 10 100 0 50 100 150 200 250 300 350 throughput (ksps) power (mw) v dd = 3v v dd = 5v figure 28. power consumption vs throughput rate
ISL267450 15 fn8341.0 august 10, 2012 serial interface conversion data is accessed with an spi-compatible serial interface. the interface consists of the serial clock (sclk), serial data output (sdata), and chip select (cs ). a falling edge on the cs signal initiates a conversion by placing the part into the acquisition (acq) phase. after t acq has elapsed, the part enters the conversion (conv) phase and begins outputting the conversion result starting with a null bit followed by the most significant bit (msb) and ending with the least significant bit (lsb). the cs pin can be pulled high at this point to put the device into standby mode and reduce the power consumption. if cs is held low after the lsb bit has been output, the conversion result will be re peated in reverse order until the msb is transmitted, after which the serial output enters a high impedance state. the ISL267450 will remain in this state, dissipating typical dynamic power levels, until cs transitions high then low to initiate the next conversion. data format output data is encoded in two?s complement format as shown in table 1. the voltage levels in the table are idealized and don?t account for any gain/offset errors or noise. application hints grounding and layout the printed circuit board that houses the ISL267450 should be designed so that the analog an d digital sections are separated and confined to certain areas of the board. this facilitates the use of ground planes that can be easily separated. a minimum etch technique is generally best for ground planes since it gives the best shielding. digital and analog ground planes should be joined in only one place, and the connection should be a star ground point established as close to the gnd pin on the ISL267450 as possible. avoid running digital lines under the device, as this will couple noise onto the die. the analog ground plane should be allowed to run under the ISL267450 to avoid noise coupling. the power supply lines to the device should use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. fast switching signals, such as clocks, should be shielded with digital ground to avoid radiating noise to other sections of the board, and clock signals should ne ver run near the analog inputs. avoid crossover of digital and analog signals. traces on opposite sides of the board should run at ri ght angles to each other. this reduces the effects of feed-t hrough through the board. a microstrip technique is by far the best but is not always possible with a double-sided board. in this technique, the component side of the board is dedicated to ground planes, while signals are placed on the solder side. good decoupling is also important. all analog supplies should be decoupled with f tantalum capacitors in parallel with 0.1 f capacitors to gnd. to achieve the best from these decoupling components, they must be placed as close as possible to the device. terminology signal-to-(noise + distortion) ratio (sinad) this is the measured ratio of sign al-to-(noise + distortion) at the output of the adc. the signal is the rms amplitude of the fundamental. noise is the sum of all nonfundamental signals up to half the sampling frequency (f s /2), excluding dc. the ratio is dependent on the number of quantization levels in the digitization process; the more levels, the smaller the quantization noise. the theoretical signal-to-(noise + distortion) ratio for an ideal n-bit converter with a sine wave input is given by equation 1: thus, for a 12-bit converter this is 74db, and for a 10-bit it is 62db. total harmonic distortion total harmonic distortion (thd) is the ratio of the rms sum of harmonics to the fundamental. fo r the ISL267450, it is defined as equation 2: where v 1 is the rms amplitude of the fundamental and v 2 , v 3 , v 4 , v 5 , and v 6 are the rms amplitudes of the second to the sixth harmonics. peak harmonic or spurious noise (sfdr) peak harmonic or spurious noise is defined as the ratio of the rms value of the next largest component in the adc output spectrum (up to fs/2 and exclud ing dc) to the rms value of the fundamental. it is also referred to as spurious free dynamic range (sfdr). normally, the valu e of this specification is determined by the largest harmonic in the spectrum, but for adcs where the harmonics are buried in the noise floor, it will be a noise peak. intermodulation distortion with inputs consisting of sine waves at two frequencies, fa and fb, any active device with nonlinearities will create distortion products at sum and difference frequencies of mfa nfb where m and n = 0, 1, 2 or 3. intermodulation distortion terms are those for which neither m nor n are equal to zero. for example, the second order terms include (fa + fb ) and (fa ? fb), while the third order terms include (2fa + fb), (2fa ? fb), (fa + 2fb), and (fa ?2fb). table 1. two?s complement data formatting input voltage digital output ?full scale ?v ref 1000 0000 0000 ?full scale + 1lsb ?v ref + 1lsb 1000 0000 0001 midscale 0 0000 0000 0000 +full scale ? 1lsb +v ref ? 1lsb 0111 1111 1110 +full scale + v ref 0111 1111 1111 signal-to-(noise + distortion) 6.02 n 1.76 + () db = (eq. 1) (eq. 2) thd db () 20 v 2 2 v 3 2 v 4 2 v 5 2 v 6 2 ++++ v 1 2 ----------------------------------------------------------------------- - log =
ISL267450 16 intersil products are manufactured, assembled and tested utilizing iso9000 quality systems as noted in the quality certifications found at www.intersil.com/design/quality intersil products are sold by description only. intersil corporat ion reserves the right to make changes in circuit design, soft ware and/or specifications at any time without notice. accordingly, the reader is cautioned to verify that data sheets are current before placing orders. information furnished by intersil is believed to be accurate and reliable. however, no responsi bility is assumed by intersil or its subsid iaries for its use; nor for any infringem ents of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of i ntersil or its subsidiaries. for information regarding intersil corporation and its products, see www.intersil.com fn8341.0 august 10, 2012 for additional products, see www.intersil.com/product_tree the ISL267450 is tested using the ccif standard, where two input frequencies near the top end of the input bandwidth are used. in this case, the second order terms are usually distanced in frequency from the original sine waves, while the third order terms are usually at a frequency close to the input frequencies. as a result, the second and th ird order terms are specified separately. the calculation of the intermodulation distortion is as per the thd specification, where it is the ratio of the rms sum of the individual distortion products to the rms amplitude of the sum of the fundamentals expressed in dbs. aperture delay this is the amount of time from the leading edge of the sampling clock until the adc actually takes the sample. aperture jitter this is the sample-to-sample vari ation in the effective point in time at which the actual sample is taken. full power bandwidth the full power bandwidth of an adc is that input frequency at which the amplitude of the reconstructed fundamental is reduced by 0.1db or 3db for a full-scale input. common-mode rejection ratio (cmrr) the common-mode rejection ratio is defined as the ratio of the power in the adc output at full-sca le frequency, f, to the power of a 200mv p-p sine wave applied to the common-mode voltage of v in+ and v in? of frequency fs as shown by equation 3.: pf is the power at the frequency f in the adc output; pfs is the power at frequency fs in the adc output. integral nonlinearity (inl) this is the maximum deviation from a straight line passing through the endpoints of the adc transfer function. differential nonlinearity (dnl) this is the difference between the measured and the ideal 1 lsb change between any two adjacent codes in the adc. zero-code error this is the deviation of the midscale code transition (111...111 to 000...000) from the ideal v in+ ? v in? (i.e., 0 lsb). positive gain error this is the deviation of the last code transition (011...110 to 011...111) from the ideal v in+ ? v in? (i.e., +v ref ? 1 lsb), after the zero code error has been adjusted out. negative gain error this is the deviation of the first code transition (100...000 to 100...001) from the ideal v in+ ? vin? (i.e., -v ref + 1 lsb), after the zero code error has been adjusted out. track and hold acquisition time the track and hold acquisition time is the minimum time required for the track and hold amplifier to remain in track mode for its output to reach and settle to within 0.5 lsb of the applied input signal. power supply rejection ratio (psrr) the power supply rejection ratio is defined as the ratio of the power in the adc output at full -scale frequency, f, to adc v dd supply of frequency f s . the frequency of this input varies from 1khz to 1mhz. pf is the power at frequency f in the adc output; pfs is the power at frequency f s in the adc output. (eq. 3) cmrr db () 10 pfl pfs ? () log = (eq. 4) psrr db () 10 pf pfs ? () log =
ISL267450 17 fn8341.0 august 10, 2012 products intersil corporation is a leader in the design and manufacture of high-performance analog semico nductors. the company's product s address some of the industry's fastest growing markets, such as , flat panel displays, cell phones, handheld products, and noteb ooks. intersil's product families address power management and analog sign al processing functions. go to www.intersil.com/products for a complete list of intersil product families. for a complete listing of applications, rela ted documentation and related parts, please see the respective device information p age on intersil.com: ISL267450 to report errors or suggestions for this datasheet, please go to: www.intersil.com/askourstaff fits are available from our website at: http://rel.intersil.co m/reports/search.php revision history the revision history provided is for inform ational purposes only and is believed to be accurate, but not warranted. please go t o web to make sure you have the latest revision. date revision change august 10, 2012 fn8341.0 initial release.
ISL267450 18 fn8341.0 august 10, 2012 package outline drawing m8.15 8 lead narrow body small outline plastic package rev 4, 1/12 detail "a" top view index area 123 -c- seating plane x 45 notes: 1. dimensioning and tolerancing per ansi y14.5m-1994. 2. package length does not include mold flash, protrusions or gate burrs. mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 3. package width does not include interlead flash or protrusions. interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per side. 4. the chamfer on the body is optional. if it is not present, a visual index feature must be located within the crosshatched area. 5. terminal numbers are shown for reference only. 6. the lead width as measured 0.36mm (0.014 inch) or greater above the seating plane, shall not exceed a maximum value of 0.61mm (0.024 inch). 7. controlling dimension: millimeter. co nverted inch dimensions are not necessarily exact. 8. this outline conforms to jedec publication ms-012-aa issue c. side view ?a side view ?b? 1.27 (0.050) 6.20 (0.244) 5.80 (0.228) 4.00 (0.157) 3.80 (0.150) 0.50 (0.20) 0.25 (0.01) 5.00 (0.197) 4.80 (0.189) 1.75 (0.069) 1.35 (0.053) 0.25(0.010) 0.10(0.004) 0.51(0.020) 0.33(0.013) 8 0 0.25 (0.010) 0.19 (0.008) 1.27 (0.050) 0.40 (0.016) 1.27 (0.050) 5.20(0.205) 1 2 3 4 5 6 7 8 typical recommended land pattern 2.20 (0.087) 0.60 (0.023)
ISL267450 19 fn8341.0 august 10, 2012 package outline drawing m8.118 8 lead mini small outline plastic package rev 4, 7/11 detail "x" side view 2 typical recommended land pattern top view pin# 1 id 0.25 - 0.36 detail "x" 0.10 0.05 (4.40) (3.00) (5.80) h c 1.10 max 0.09 - 0.20 33 gauge plane 0.25 0.95 ref 0.55 0.15 b 0.08 c a-b d 3.00.05 12 8 0.85010 seating plane a 0.65 bsc 3.00.05 4.90.15 (0.40) (1.40) (0.65) d 5 5 side view 1 dimensioning and tolerancing conform to jedec mo-187-aa plastic interlead protrusions of 0.15mm max per side are not dimensions in ( ) are for reference only. dimensions are measured at datum plane "h". plastic or metal protrusions of 0.15mm max per side are not dimensions are in millimeters. 3. 4. 5. 6. notes: 1. 2. and amsey14.5m-1994. included. included. 0.10 c m

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