$ figure 1. ads-926 functional block diagram ref register register 18 bit 1 (msb) 17 bit 2 12 t i b 3 11 bit 4 10 bit 5 9 bit 6 8 bit 7 7 bit 8 6 bit 9 5 bit 10 4 bit 11 3 bit 12 2 bit 13 1 bit 14 (lsb ) timing and control logic +10v ref. out 21 start convert 16 eoc 15 digital correction logic dac flash adc buffer C + s/h analog input 20 13 +5v supply 22 +12v/+15v supply 19, 23 analog ground 14 digital ground 24 C12v/C15v supply s 2 s 1 block diagram the ads-926 is a high-performance, 14-bit, 500khz sampling a/d converter. this device accurately samples full-scale input signals up to nyquist frequencies with no missing codes and exhibits outstanding dynamic performance that surpasses most 16-bit, 500khz sampling a/d's. thd and snr, for example, are typically C90db and 80db when converting fullscale input signals up to 100khz. housed in a small 24-pin ddip or smt (gull- wing) package, the functionally complete ads-926 contains a fast-settling sample-hold ampli? er, a subranging (two-pass) a/d converter, a precise voltage reference, timing/control logic, and error- correction circuitry. digital input and output levels are ttl. requiring 15v (or 12v) and +5v supplies, the ads-926 dissipates only 1.75w (1.6w for 12v), maximum. the unit is offered with a bipolar input (C5v to +5v). models are available for use in either commercial (0 to +70c) or military (C55 to +125c) operating temperature ranges. applications include radar, sonar, spectrum analysis, and graphic/medical imaging. contact datel for information on devices screened to mil-std-883. product overview features 14-bit resolution 500khz sampling rate functionally complete; no missing codes small 24-pin ddip or smt package operates from 15v or 12v supplies +5v supply low power, 1.75 watts maximum samples up to nyquist frequencies outstanding dynamic performance bipolar 5v input range input/output connections pin function pin function 1 bit 14 (lsb) 24 C12v/C15v supply 2 bit 13 23 analog ground 3 bit 12 22 +12v/+15v supply 4 bit 11 21 +10v reference out 5 bit 10 20 analog input 6 bit 9 19 analog ground 7 bit 8 18 bit 1 (msb) 8 bit 7 17 bit 2 9 bit 6 16 start convert 10 bit 5 15 eoc 11 bit 4 14 digital ground 12 bit 3 13 +5v supply for full details go to www.murata-ps.com/rohs www.murata-ps.com www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 1 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
physical/environmental parameters min. typ. max. units operating temp. range, case ads-926mc, gc 0 +70 c ads-926mm, gm C55 +125 c thermal impedance jc 6 c/watt ca 24 c/watt storage temperature range C65 +150 c package type 24-pin, metal-sealed, ceramic ddip or smt weight 0.42 ounces (12 grams) absolute maximum ratings parameters limits units +12v/+15v supply (pin 22) 0 to +16 volts C12v/C15v supply (pin 24) 0 to C16 volts +5v supply (pin 13) 0 to +6 volts digital input (pin 16) C0.3 to +v dd +0.3 volts analog input (pin 20) 15 volts lead temperature (10 seconds) +300 c +25c 0 to +70c C55 to +125c analog input min. typ. max. min. typ. max. min. typ. max. units input voltage range ? 5 5 5 volts input resistance 1 1 1 k input capacitance 7 15 7 15 7 15 pf digital input logic levels logic "1" +2.0 +2.0 +2.0 volts logic "0" +0.8 +0.8 +0.8 volts logic loading "1" +20 +20 +20 a logic loading "0" C20 C20 C20 a start convert positive pulse width ? 175 200 225 175 200 225 175 200 225 ns static performance resolution 14 14 14 bits integral nonlinearity (f in = 10khz) 0.5 0.75 1.5 lsb differential nonlinearity (f in = 10khz) 0.5 +0.95 0.5 0.95 0.75 +0.99 lsb full scale absolute accuracy 0.08 0.15 0.15 0.25 0.3 0.5 %fsr bipolar zero error (tech note 2) 0.05 0.1 0.1 0.25 0.15 0.3 %fsr bipolar offset error (tech note 2) 0.05 0.1 0.1 0.25 0.25 0.5 %fsr gain error (tech note 2) 0.1 0.15 0.15 0.25 0.25 0.5 %fsr no missing codes (f in = 10khz) 14 14 14 bits dynamic performance peak harmonics (C0.5db) dc to 100khz C92 C88 C90 C85 C88 C81 db 100khz to 250khz C90 C85 C90 C85 C86 C80 db total harmonic distortion (C0.5db) dc to 100khz C90 C86 C89 C82 C87 C78 db 100khz to 250khz C87 C82 C87 C82 C81 C76 db signal-to-noise ratio (w/o distortion, C0.5db) dc to 100khz 78 80 78 80 74 78 db 100khz to 250khz 78 80 78 80 74 77 db signal-to-noise ratio ? (& distortion, C0.5db) dc to 100khz 77 79 77 79 74 78 db 100khz to 250khz 77 79 77 79 73 77 db two-tone intermodulation distortion (f in = 100khz, 240khz, f s = 500khz C0.5db) C87 C86 C85 db noise 300 300 350 vrms input bandwidth (C3db) small signal (C20db input) 7 7 7 mhz large signal (C0.5db input) 3 3 3 mhz feedthrough rejection (f in = 250khz) 84 84 84 db slew rate 40 40 40 v/s aperture delay time 20 20 20 ns aperture uncertainty 50 50 50 ps rms s/h acquisition time (to 0.003%fsr, 10v step) 1335 1390 1445 1335 1390 1445 1335 1390 1445 ns overvoltage recovery time ? 1400 2000 1400 2000 1400 2000 ns a/d conversion rate 500 500 500 mhz functional specifications (t a = +25c, v cc = 15v (or 12v), +v dd = +5v, 500khz sampling rate, and a minimum 1 minute warmup ? unless otherwise speci? ed.) www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 2 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
technical notes +25c 0 to +70c C55 to +125c analog output min. typ. max. min. typ. max. min. typ. max. units internal reference voltage +9.95 +10.0 +10.05 +9.95 +10.0 +10.05 +9.95 +10.0 +10.05 volts drift 5 5 5 ppm/c external current 1.5 1.5 1.5 ma digital outputs logic levels logic "1" +2.4 +2.4 +2.4 volts logic "0" +0.4 +0.4 +0.4 volts logic loading "1" C4 C4 C4 ma logic loading "0" +4 +4 +4 ma delay, falling edge of eoc to output data valid 35 35 35 ns output coding offset binary power requirements , 15v power supply ranges +15v supply +14.5 +15.0 +15.5 +14.5 +15.0 +15.5 +14.5 +15.0 +15.5 volts C15v supply C14.5 C15.0 C15.5 C14.5 C15.0 C15.5 C14.5 C15.0 C15.5 volts +5v supply +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 volts power supply currents +15v supply +41 +63 +41 +63 +41 +63 ma C15v supply C23 C40 C23 C40 C23 C40 ma +5v supply +71 +85 +71 +85 +71 +85 ma power dissipation 1.4 1.75 1.4 1.75 1.4 1.75 watts power supply rejection 0.02 0.02 0.02 %fsr/%v power requirements, 12v power supply ranges +12v supply +14.5 +15.0 +15.5 +14.5 +15.0 +15.5 +14.5 +15.0 +15.5 volts C12v supply C14.5 C15.0 C15.5 C14.5 C15.0 C15.5 C14.5 C15.0 C15.5 volts +5v supply +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 volts power supply currents +12v supply +41 +60 +41 +60 +41 +60 ma C12v supply C23 C40 C23 C40 C23 C40 ma +5v supply +71 +85 +71 +85 +71 +85 ma power dissipation 1.3 1.6 1.3 1.6 1.3 1.6 watts power supply rejection 0.02 0.02 0.02 %fsr/%v footnotes: ? all power supplies must be on before applying a start convert pulse. all supplies and the clock (start convert) must be present during warmup periods. the device must be continuously converting during this time. ? see ordering information for 0 to +10v input range. contact datel for availability of other input voltage ranges. ? a 500khz clock with a 200ns wide start convert pulse is used for all production testing. for applications requiring less than a 500khz sampling rate, wider start convert pulses can be used. see timing diagram for more details. ? this is the time required before the a/d output data is valid after the analog input is back within the speci? ed range. (snr + distortion) C 1.76 + 20 log full scale amplitude actual input amplitude 6.02 ? effective bits is equal to: 1. obtaining fully speci? ed performance from the ads-926 requires care- ful attention to pc-card layout and power supply decoupling. the device's analog and digital ground systems are connected to each other internally. for optimal performance, tie all ground pins (14, 19 and 23) directly to a large analog ground plane beneath the package. bypass all power supplies and the reference output (pin 21) to ground with 4.7f tantalum capacitors in parallel with 0.1f ceramic capacitors. locate the bypass capacitors as close to the unit as possible. if the user- installed offset and gain adjusting circuit shown in figure 2 is used, also locate it as close to the ads-926 as possible. 2. the ads-926 achieves its speci? ed accuracies without the need for exter- nal calibration. if required, the device's small initial offset and gain errors can be reduced to zero using the input circuit of figure 2. when using this circuit, or any similar offset and gain-calibration hardware, make adjust- ments following warmup. to avoid interaction, always adjust offset before gain. 3. when operating the ads-926 from 12v supplies, do not drive external circuitry with the reference output. the reference's accuracy and drift speci? cations may not be met, and loading the circuit may cause accuracy errors within the converter. 4. applying a start convert pulse while a conversion is in progress (eoc = logic "1") initiates a new and inaccurate conversion cycle. data from the interrupted and subsequent conversions will be invalid. www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 3 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
to pin 20 of ads-926 15v signal input gain adjust 1.98k 50 +15v 2k 1.2m 20k C15v +15v zero/ offset adjust figure 2. ads-926 calibration circuit 13 ads-926 14 20 16 18 17 12 11 10 9 8 7 6 5 4 3 2 1 15 bit 1 (msb) bit 2 bit 3 bit 4 bit 5 bit 6 bit 7 bit 8 bit 9 bit 10 bit 11 bit 12 bit 13 bit 14 (lsb) eoc analog input start convert 19, 23 22 24 0.1f 4.7f +5v 0.1f 4.7f 0.1f 4.7f + + C 12v/C15v +12v/+15v + 0.1f + 4.7f 21 +10v ref. out C5v to +5v digital ground analog ground figure 3. typical ads-926 connection diagram calibration procedure (refer to figures 2 and 3) any offset and/or gain calibration procedures should not be implemented until devices are fully warmed up. to avoid interaction, offset must be adjusted before gain. the ranges of adjustment for the circuit of figure 2 are guaranteed to compensate for the ads-926's initial accuracy errors and may not be able to compensate for additional system errors. all ? xed resistors in figure 2 should be metal-? lm types, and multiturn potentiometers should have tcrs of 100ppm/c or less to minimize drift with temperature. a/d converters are calibrated by positioning their digital outputs exactly on the transition point between two adjacent digital output codes. this can be accomplished by connecting led's to the digital outputs and adjusting until certain led's "? icker" equally between on and off. other approaches employ digital comparators or microcontrollers to detect when the outputs change from one code to the next. for the ads-926, offset adjusting is normally accomplished at the point where the msb is a 1 and all other output bits are 0's and the lsb just changes from a 0 to a 1. this digital output transition ideally occurs when the applied analog input is +? lsb (+305v). gain adjusting is accomplished when all bits are 1's and the lsb just changes from a 1 to a 0. this transition ideally occurs when the analog input is at +full scale minus 1? lsb's (+4.999085v). zero/offset adjust procedure 1. apply a train of pulses to the start convert input (pin 16) so the con- verter is continuously converting. if using led's on the outputs, a 200khz conversion rate will reduce ? icker. 2. apply +305v to the analog input (pin 20). 3. adjust the offset potentiometer until the output bits are a 1 and all 0's and the lsb ? ickers between 0 and 1. gain adjust procedure 1. 1. apply +4.999085v to the analog input (pin 20). 2. adjust the gain potentiometer until the output bits are all 1's and the lsb ? ickers between 1 and 0. table 2. output coding output coding input range 5v bipolar scale msb lsb 11 1111 1111 1111 +4.99939 +fs C1 lsb 11 1000 0000 0000 +3.75000 +3/4 fs 11 0000 0000 0000 +2.50000 +1/2fs 10 0000 0000 0000 0.00000 0 01 0000 0000 0000 C2.50000 C1/2fs 00 1000 0000 0000 C3.75000 C3/4fs 00 0000 0000 0001 C4.99939 Cfs +1 lsb 00 0000 0000 0000 C5.00000 Cfs coding is offset binary; 1lsb = 610v. table 1. zero and gain adjust input voltage range zero adjust +? lsb gain adjust +fs C1? lsb 5v +305v +4.999085v www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 4 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
notes: 1. f s = 500khz. 2. the ads-926 is a pulse-triggered device. its internal operations are triggered by both the rising and falling edges of the start convert pulse. when sampling at 500khz, the start pulse must be between 175 and 225nsec wide. for lower sampling rates, wider start pulses may be used, however, a 50nsec minimum pulse width low must be maintained. start convert output data internal s/h n n + 1 data (n C 1) valid acquisition time 10ns typ. data n valid (1885ns min.) eoc conversion time invalid data 115ns max. 10ns typ. 1390ns 55ns 35ns max. hold 200ns 25ns 610ns typ. 480ns 20ns 70ns 10ns figure 4. ads-926 timing diagram devices do not overheat. the ground and power planes beneath the package, as well as all pcb signal runs to and from the device, should be as heavy as possible to help conduct heat away from the package. electrically-insulating, thermally-conductive "pads" may be installed underneath the package. devices should be soldered to boards rather than "socketed," and of course, minimal air ? ow over the surface can greatly help reduce the package temperature. thermal requirements all datel sampling a/d converters are fully characterized and speci- ? ed over operating temperature (case) ranges of 0 to +70c and C55 to +125c. all room-temperature (t a = +25c) production testing is performed without the use of heat sinks or forced-air cooling. thermal impedance ? gures for each device are listed in their respective speci? ca- tion tables. these devices do not normally require heat sinks; however, standard precautionary design and layout procedures should be used to ensure www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 5 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
figure 5. ads-926 evaluation board schematic www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 6 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
figure 6. ads-926 fft analysis 0 C10 C20 C30 C40 C50 C60 C70 C80 C90 C100 C110 C120 C130 C140 C150 frequency (khz) (fs = 500khz, fin = 240khz, vin = C0.5db, 16,384-point fft) amplitude relative to full scale (db) 0 25 50 75 100 125 150 175 200 225 250 figure 7. ads-926 histogram and differential nonlinearity 0 number of occurrences digital output code 0 16,384 +0.59 0 C0.57 16,384 dnl (lsb's) digital output code www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 7 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
mechanical dimensions - inches (mm) ordering information model number operating temp. range analog input accessories ads-926mc 0 to +70c bipolar (5v) ads-b926/927 evaluation board (without ads-926) ads-926mm C55 to +125c bipolar (5v) hs-24 heat sinks for all ads-916/926 ddip models. ads-926/883 C55 to +125c bipolar (5v) receptacles for pc board mounting can be ordered through amp inc. part #3-331272-8 (component lead socket), 24 required. for mil-std-883 product speci? cations, contact datel. * for information, see ads-916 data sheet. ads-926gc 0 to +70c bipolar (5v) ads-926gm C55 to +125c bipolar (5v) ads-916mc 0 to +70c unipolar (0 to +10v)* ads-916mm C55 to +125c unipolar (0 to +10v)* ads-916gc 0 to +70c unipolar (0 to +10v)* ads-916gm C55 to +125c unipolar (0 to +10v)* 0.200 max. (5.080) 0.235 max. (5.969) 0.600 0.010 (15.240) 0.80 max. (20.32) 0.100 typ. (2.540) 0.100 (2.540) 0.018 0.002 (0.457) 0.100 (2.540) 0.040 (1.016) 1.31 max. (33.27) 112 13 24 1.100 (27.940) 0.190 max. (4.826) 0.010 (0.254) +0.002 C0.001 seating plane 0.025 (0.635) dimension tolerances (unless otherwise indicated): 2 place decimal (.xx) 0.010 (0.254) 3 place decimal (.xxx) 0.005 (0.127) lead material: kovar alloy lead finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating pin 1 index 24-pin ddip versions ads-926mc ads-926mm ads-926/883 ads-916mc ads-916mm 24-pin surface mount versions ads-926gc ads-926gm ads-916gc ads-916gm 0.80 max. (20.32) 0.015 (0.381) max. radius for any pin 1.31 max. (33.02) 0.100 typ. (2.540) 0.100 (2.540) 0.190 max. (4.826) 0.040 (1.016) 0.020 typ. (0.508) 0.020 (0.508) 24 13 12 1 pin 1 index 0.130 typ. (3.302) dimension tolerances (unless otherwise indicated): 2 place decimal (.xx) 0.010 (0.254) 3 place decimal (.xxx) 0.005 (0.127) lead material: kovar alloy lead finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating 0.060 typ. (1.524) 0.010 typ. (0.254) www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 8 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
murata power solutions, inc. makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. the descriptions contained her ein do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. speci? cations are subject to cha nge without notice. ? 2009 murata power solutions, inc. usa: mans? eld (ma), tel: (508) 339-3000, email: sales@murata-ps.com canada: toronto, tel: (866) 740-1232, email: toronto@murata-ps.com uk: milton keynes, tel: +44 (0)1908 615232, email: mk@murata-ps.com france: montigny le bretonneux, tel: +33 (0)1 34 60 01 01, email: france@murata-ps.com germany: mnchen, tel: +49 (0)89-544334-0, email: munich@murata-ps.com japan: tokyo, tel: 81-3-3779-1031, email: japan@murata-ps.com kyoto, tel: 81-75-955-7269, email: japan@murata-ps.com china: shanghai, tel: +86 215 027 3678, email: shanghai@murata-ps.com guangzhou, tel: +86 208 221 8066, email: guangzhou@murata-ps.com singapore: parkway centre, tel: +65 6348 9096, email: singapore@murata-ps.com murata power solutions, inc. 11 cabot boulevard, mans? eld, ma 02048-1151 u.s.a. tel: (508) 339-3000 (800) 233-2765 fax: (508) 339-6356 www.murata-ps.com email: sales@murata-ps.com iso 9001 and 14001 registered 07/24/09 www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-926.b01 page 9 of 9 ads-926 14-bit, 500khz, low-power sampling a/d converters
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