$ figure 1. ads-946 functional block diagram ref dac register register output register 16 bit 14 (lsb) 15 bit 13 12 bit 12 11 bit 11 10 bit 10 9 bit 9 8 bit 8 7 bit 7 6 bit 6 5 bit 5 4 bit 4 3 bit 3 2 bit 2 1 bit 1 (msb) timing and control logic offset adjust 23 analog input 21 start convert 18 eoc 17 +5v analog supply 22 +5v digital supply 13 C5v supply 20 analog ground 19, 24 digital ground 14 C + s/h buffer digital correction logic flash adc 1 flash adc 2 power and grounding amp block diagram the low-cost ads-946 is a 14-bit, 8mhz sam- pling a/d converter. this device accurately samples full-scale input signals up to nyquist frequencies with no missing codes. excellent differential nonlin- earity error (dnl), signal-to-noise ratio (snr), and total harmonic distortion (thd) make the ads-946 the ideal choice for both time-domain (ccd/fpa imaging, scanners, process control) and frequency- domain (radar, telecommunications, spectrum analysis) applications. the functionally complete ads-946 contains a fast-settling sample-hold ampli? er, a subranging (two-pass) a/d converter, an internal reference, timing/control logic, and error-correction circuitry. digital input and output levels are ttl. the ads- 946 only requires the rising edge of a start convert pulse to operate. requiring only 5v supplies, the ads-946 typically dissipates just 2 watts. the device is offered with a bipolar input range of 2v. models are available for use in either commercial (0 to +70c) or hi-rel (C55 to +125c) operating temperature ranges. a proprietary, auto-calibrating, error-correcting circuit allows the device to achieve speci? ed performance over the full hi-rel tem- perature range. product overview input/output connections pin function pin function 1 bit 1 (msb) 24 analog ground 2 bit 2 23 offset adjust 3 bit 3 22 +5v analog supply 4 bit 4 21 analog input 5 bit 5 20 C5v supply 6 bit 6 19 analog ground 7 bit 7 18 start convert 8 bit 8 17 eoc 9 bit 9 16 bit 14 (lsb) 10 bit 10 15 bit 13 11 bit 11 14 digital ground 12 bit 12 13 +5v digital supply features 14-bit resolution 8mhz guaranteed sampling rate no missing codes over full hi-rel temperature range ideal for both time and frequency-domain applications excellent thd (C75db) and snr (77db) edge-triggered; no pipeline delays small, 24-pin, ceramic ddip or smt requires only 5v supplies low-power, 2 watts mil-std-883 screening available 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-946.b01 page 1 of 9 ads-946 14-bit, 8mhz sampling a/d converters
physical/environmental parameters min. typ. max. units operating temp. range, case ads-946 0 +70 c ads-946ex C55 +125 c thermal impedance jc 6 c/watt ca 23 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 +5v supply (pins 13, 22) 0 to +6 volts C5v supply (pin 20) 0 to C6 volts digital input (pin 18) C0.3 to +v dd +0.3 volts analog input (pin 21) 5 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 2 2 2 volts input resistance 200 200 200 input capacitance 6 15 6 15 6 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 ? 10 20 10 20 10 20 ns static performance resolution 14 14 14 bits integral nonlinearity (? n = 10khz) 0.75 0.75 1 lsb differential nonlinearity (? n = 10khz) C0.95 0.5 +1.25 C0.95 0.5 +1.25 C0.95 0.75 +1.5 lsb full scale absolute accuracy 0.15 0.4 0.15 0.4 0.4 0.8 %fsr bipolar zero error (tech note 2) 0.2 0.4 0.2 0.4 0.4 0.65 %fsr gain error (tech note 2) 0.2 0.75 0.2 0.75 0.4 1.25 % no missing codes (? n = 10khz) 14 14 14 bits dynamic performance peak harmonics (C0.5db) dc to 500khz C76 C72 C76 C72 C74 C70 db 500khz to 1mhz C75 C72 C75 C72 C74 C68 db 1mhz to 4mhz C75 C71 C75 C71 C69 C65 db total harmonic distortion (C0.5db) dc to 500khz C75 C71 C75 C71 C74 C70 db 500khz to 1mhz C75 C70 C75 C70 C72 C68 db 1mhz to 4mhz C75 C70 C75 C70 C69 C64 db signal-to-noise ratio (w/o distortion, C0.5db) dc to 500khz 73 77 73 77 72 76 db 500khz to 1mhz 73 77 73 77 72 76 db 1mhz to 4mhz 73 77 73 77 71 76 db signal-to-noise ratio (& distortion, C0.5db) dc to 500khz 70 74 70 74 68 73 db 500khz to 1mhz 69 73 69 73 65 70 db 1mhz to 4mhz 69 73 69 73 65 70 db noise 150 150 150 vrms two-tone intermodulation distortion (? n = 2.45mhz, 1.975mhz, fs = 8mhz, C0.5db) C82 C82 C82 db input bandwidth (C3db) small signal (C20db input) 30 30 30 mhz large signal (C0.5db input) 10 10 10 mhz feedthrough rejection (? n = 4mhz) 85 85 85 db slew rate 400 400 400 v/s aperture delay time +5 +5 +5 ns aperture uncertainty 2 2 2 ps rms s/h acquisition time (to 0.003%fsr, 4v step) 55 60 55 60 55 60 ns overvoltage recovery time ? 100 125 100 125 100 125 ns a/d conversion rate 8 8 8 mhz functional specifications (t a = +25c, v dd = 5v, 8mhz sampling rate, and a minimum 3 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-946.b01 page 2 of 9 ads-946 14-bit, 8mhz sampling a/d converters
technical notes footnotes: ? all power supplies should be on before applying a start convert pulse. all supplies and the clock (start convert pulses) must be present during warmup periods. the device must be continuously converting during this time. ? contact datel for other input voltage ranges. ? an 8mhz clock with a 20nsec positive pulse width is used for all production testing. see timing diagram, figure 4, for more details. ? effective bits is equal to: ? this is the time required before the a/d output data is valid once the analog input is back within the speci? ed range. this time is only guaranteed if the input does not exceed 2.2v (s/h saturation voltage). ? the minimum supply voltages of +4.9v and C4.9v for vdd are required for C55c operation only. the minimum limits are +4.75v and C4.75v when operating at +125c. (snr + distortion) C 1.76 + 20 log full scale amplitude actual input amplitude 6.02 1. obtaining fully speci? ed performance from the ads-946 requires care- ful attention to pc card layout and power supply decoupling. the devices analog and digital ground systems are connected to each other internally. for optimal performance, tie all ground pins (14, 19 and 24) directly to a large analog ground plane beneath the package. bypass all power supplies 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. 2. the ads-946 achieves its speci? ed accuracies without the need for exter- nal calibration. if required, the devices small initial offset and gain errors can be reduced to zero using the adjustment circuitry shown in figures 2 and 3. when using this circuitry, or any similar offset and gain calibra- tion hardware, make adjustments following warmup. to avoid interaction, always adjust offset before gain. 3. applying a start convert pulse while a conversion is in progress (eoc = logic 1) will initiate a new and inaccurate conversion cycle. data for the interrupted and subsequent conversions will be invalid. 4. a passive bandpass ? lter is used at the input of the a/d for all production testing. +25c 0 to +70c C55 to +125c digital outputs min. typ. max. min. typ. max. min. typ. max. units 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 output coding offset binary power requirements power supply ranges ? +5v supply +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 +4.9 +5.0 +5.25 volts C5v supply C4.75 C5.0 C5.25 C4.75 C5.0 C5.25 C4.9 C5.0 C5.25 volts power supply currents +5v supply +270 +290 +270 +290 +270 +290 ma C5v supply C150 C170 C150 C170 C150 C170 ma power dissipation 2 2.3 2 2.3 2 2.3 watts power supply rejection 0.05 0.05 0.05 %fsr/%v to pin 21 of ads-946 C5v signal input gain adjust 1.98k 50 +5v 2k figure 2. optional ads-946 gain adjust calibration circuit www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-946.b01 page 3 of 9 ads-946 14-bit, 8mhz sampling a/d converters
calibration procedure 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 circuits in figures 2 and 3 are guaranteed to compensate for the ads-946's initial accuracy errors and may not be able to compensate for additional system errors. 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 leds 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. offset adjusting for the ads-946 is normally accomplished at the point where the msb is a 1 and all other output bits are 0s and the lsb just changes from a 0 to a 1. this digital output transition ideally occurs when the applied analog input is +? lsb (+122v). 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 (+1.99963v). zero/offset adjust procedure 1. apply a train of pulses to the start convert input (pin 18) so the con- verter is continuously converting. 2. apply +122v to the analog input (pin 21). 3. adjust the offset potentiometer until the output bits are 10 0000 0000 0000 and the lsb ? ickers between 0 and 1. gain adjust procedure 1. apply +1.99963v to the analog input (pin 21). 2. adjust the gain potentiometer until all output bits are 1's and the lsb ? ick- ers between 1 and 0. 3. to con? rm proper operation of the device, vary the input signal to obtain the output coding listed in table 2. 0.1f 0.1f 4.7f 4.7f 22, 13 24 20 19 ads-946 C5v 20k 0.1f 4.7f +5v 14 C5v +5v 21 23 18 1 2 3 4 5 6 7 8 9 10 11 12 15 16 17 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 a single +5v supply should be used for both the +5v analog and +5v digital. if se p arate su pp lies are used, the difference between the two cannot exceed 100mv. ~ ~ + + + zero/ offset adjust figure 3. typical ads-946 connection diagram table 2. output coding for bipolar operation bipolar scale input range (2v range) offset binary msb lsb +fs C1 lsb +1.99976 11 1111 1111 1111 +3/4 fs +1.50000 11 1000 0000 0000 +1/2 fs +1.00000 11 0000 0000 0000 0 0.00000 10 0000 0000 0000 C1/2 fs C1.00000 01 0000 0000 0000 C3/4 fs C1.50000 00 1000 0000 0000 Cfs +1 lsb C1.99976 00 0000 0000 0001 Cfs C2.00000 00 0000 0000 0000 table 1. gain and zero adjust input voltage range zero adjust +? lsb gain adjust +fs C1? lsb 2v +122v +1.99963v www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-946.b01 page 4 of 9 ads-946 14-bit, 8mhz sampling a/d converters
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 (ta = +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? cation tables. these devices do not normally require heat sinks, however, standard precau- tionary design and layout procedures should be used to ensure 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 under- neath 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. figure 4. ads-946 timing diagram notes: 1. scale is approximately 5ns per division. sampling rate = 8mhz. 2. the start convert positive pulse width must be between 10 and 50ns or between 80 and 110ns (when sampling at 8mhz) to ensure proper operation. for sampling rates less than 8mhz, the start pulse can be wider than 110nsec, however a minimum pulse width low of 15nsec should be maintained. an 8mhz clock with a 20nsec positive pulse width is used for all production testing. start convert internal s/h nn+1 20ns typ. 25ns typ. acquisition time 55ns typ. 60ns max. hold 10ns typ. eoc 20ns typ. conversion time 78ns min., 85ns typ., 90ns max. output data data n-1 valid data n valid 30ns typ. invalid data 95ns typ. 70ns typ. 10ns typ. www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-946.b01 page 5 of 9 ads-946 14-bit, 8mhz sampling a/d converters
figure 5. fft analysis of ads-946 0 C10 C20 C30 C40 C50 C60 C70 C80 C90 C100 C110 C120 C130 C140 C150 amplitude relative to full scale (db) frequency (fs = 8mhz, fin = 3.85mhz, vin = C0.5db, 16,384-point fft) 0 400 800 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 khz khz mhz mhz mhz mhz mhz mhz mhz mhz figure 6. ads-946 histogram and differential nonlinearity dnl (lsb's) codes 0 16,384 C0.57 +0.81 0 16,384 digital output code number of occurrences www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-946.b01 page 6 of 9 ads-946 14-bit, 8mhz sampling a/d converters
figure 7. ads-946 evaluation board schematic (ads-b946) gnd q clr ck d pr +5vf +5va +15v C15v -15v +15v C5va +5v C5v +5vf -15v -5va option +5vf q pr d ck clr +5vf +5vf +5vf +5v C5v +5va bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 ads-946 +5vd dgnd bit13 bit14 eoc trig agnd -5v ain +5va offset agnd q1 q2 q3 q4 q5 q6 q7 q8 8d 7d 6d 5d 4d 3d 2d 1d + + + + + + + C +5va +15v + + + + + c15 u6 p2 sg10 sg3 sg2 sg1 c14 c7 c13 c6 c12 c5 l7 l6 r1 c20 c4 c11 l5 l4 l3 c3 c10 c2 c9 l2 c8 c1 l1 p4 c19 sg8 sg7 u4 r2 c18 sg5 sg6 sg4 r3 c26 c27 c25 sg9 c24 c23 c16 c22 c17 c21 x1 u6 p3 jpr1 u5 p1 jpr2 u5 u1 u3 offset adjust ana. in in ana. clc402 hi2541 ana. in start convert 7 8 14 conv. start 74hct86 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 trig 74hct86 74hct573 74hct573 74hct86 hct7474 20h 20h 20k 20 h 20h 20h 20h 20h hct7474 8mhz crystal 15pf 3.2k 2.2f 4 5 6 13 12 14 11 7 9 8 13 11 12 10 26 24 22 25 23 21 19 17 15 13 11 9 7 5 3 1 20 18 16 14 12 10 8 6 4 2 2 5 4 11 10 14 5 6 4 2 3 1 7 2 3 1 2 1 3 33 31 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1 2 3 1 9 10 8 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 19 18 17 16 15 14 13 10 1 12 13 14 15 16 17 18 19 20 2 3 4 5 6 7 8 9 11 spare gates c1 - c7 are 20v. 2. close sg1-sg3, sg9, sg10. all resistors are in ohms. 1. unless otherwise specified all capacitors are 50v. notes: oe ce q1 q2 q3 q4 q5 q6 q7 q8 8d 7d 6d 5d 4d 3d 2d 1d u2 10 12 13 14 15 16 17 18 19 20 2 3 4 5 6 7 8 9 11 oe ce 1 ce 0.1f 0.1f 0.1f 0.1f 0.1f 2.2f 0.1f 2.2f 2.2f 0.1f 2.2f 2.2f 2.2f 2.2f 2.2f 2.2f 2.2f 6 +5vf (optional) (optional) (optional) (optional) 0.01f 0.01f 0.01f 0.01f 0.01f 0.01f 0.01f 0.1f u5 u5 q 3. see datel dwg a-24546 for additional information on ads-b946 evaluation board. www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-946.b01 page 7 of 9 ads-946 14-bit, 8mhz sampling a/d converters
mechanical dimensions inches (mm) 24-pin ddip versions ads-946mc ads-946mm ads-946/883 24-pin surface mount versions ads-946gc ads-946gm ads-946g/883 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 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-946.b01 page 8 of 9 ads-946 14-bit, 8mhz sampling a/d converters
ordering information model number operating temp. range 24-pin package accessories ads-946mc 0 to +70c ddip ads-b946 evaluation board (without ads-946) ads-946mm C55 to +125c ddip hs-24 heat sink for all ads-946 ddip models ads-946/883 C55 to +125c ddip 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 specifcation, contact datel. ads-946gc 0 to +70c smt ads-946gm C55 to +125c smt ads-946g/883 C55 to +125c smt 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 08/12/09 www.murata-ps.com technical enquiries email: data.acquisition@murata-ps.com, tel: +1 508 339 3000 mda_ads-946.b01 page 9 of 9 ads-946 14-bit, 8mhz sampling a/d converters
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