features ? ? ? ? ? 18-bit resolution ? ? ? ? ? 1mhz minimum sampling rate ? ? ? ? ? no missing codes over full military temperature range ? ? ? ? ? very low power, 1.45 watts ? ? ? ? ? small, 32-pin, side-brazed, ceramic tdip ? ? ? ? ? edge-triggered ? ? ? ? ? excellent performance ? ? ? ? ? ideal for both time and frequency-domain applications ? ? ? ? ? low cost operating temperature ranges. a proprietary, auto-calibrating, error-correcting circuit enables the device to achieve specified performance over the full military temperature range. preliminary product data ads-951 18-bit, 1mhz, low-power sampling a/d converters general description the low-cost ads-951 is an 18-bit, 1mhz sampling a/d converter. this device accurately samples full-scale input signals up to nyquist frequencies with no missing codes. this feature, combined with excellent signal-to-noise ratio (snr) and total harmonic distortion (thd), makes the ads-951 the ideal choice for both time-domain (medical imaging, scanners, process control) and frequency-domain (radar, telecommunica- tions, spectrum analysis) applications. packaged in a 32-pin, side-brazed, metal-sealed, ceramic tdip, the functionally complete ads-951 contains a fast- settling sample-hold amplifier, a subranging (two-pass) a/d converter, an internal reference, timing/control logic, and error- correction circuitry. digital input and output levels are ttl, and the ads-951 only requires the rising edge of the start convert pulse to operate. requiring 15v and 5v supplies, the ads-951 typically dissipates 1.45 watts. the device is offered with a bipolar (5v) analog input range. models are available for use in either commercial (0 to +70c) or military (?55 to +125c) input/output connections figure 1. ads-951 functional block diagram 1 bit 2 32 bit 3 2 bit 1 (msb) 31 bit 4 3 analog ground 30 bit 5 4 analog input 29 bit 6 5 +5v reference out 28 bit 7 6 gain adjust 27 bit 8 7 compensation 26 bit 9 8 ?15v supply 25 bit 10 9 +15v supply 24 bit 11 10 +5v analog supply 23 bit 12 11 ?5v analog supply 22 bit 13 12 analog ground 21 bit 14 13 digital ground 20 bit 15 14 +5v digital supply 19 bit 16 15 eoc 18 bit 17 16 start convert 17 bit 18 (lsb) pin function pin function datel, inc., mansfield, ma 02048 (usa) ? tel: (508) 339-3000, (800) 233-2765 fax: (508) 339-6356 ? email: sales@datel.com ? internet: www.datel.com ?? ref dac 2 bit 1 (msb) 1 bit 2 32 bit 3 31 bit 4 30 bit 5 29 bit 6 28 bit 7 27 bit 8 26 bit 9 25 bit 10 24 bit 11 23 bit 12 22 bit 13 21 bit 14 20 bit 15 19 bit 16 18 bit 17 17 bit 18 (lsb) timing and control logic analog input 4 start convert 16 eoc 15 ? + s/h buffer digital correction logic flash adc 1 flash adc 2 amp gain circuit compensation 7 + 5v reference out 5 10 +5v analog supply 11 ? 5v analog supply 3, 12 analog ground 14 +5v digital supply 9 +15v supply 8 ? 15v supply 13 digital ground gain adjust 6
ads-951 2 ?? +25c 0 to +70c ?55 to +125c analog input min. typ. max. min. typ. max. min. typ. max. units input voltage range ? ? 5 ?? 5 ?? 5 ? volts input resistance ? 500 ?? 500 ?? 500 ? ? input capacitance ? 715 ? 715 ? 715pf 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" ??? 20 ??? 20 ??? 20 a start convert positive pulse width ? 20 500 ? 20 500 ? 20 500 ? ns static performance resolution ? 18 ?? 18 ?? 18 ? bits integral nonlinearity (f in = 10khz) ? 0.75 ?? 1.5 ?? 2 ? lsb differential nonlinearity (f in = 10khz) ? 0.95 0.5 +1 ? 0.95 0.5 +1 ? 0.95 0.50 +1.25 lsb full scale absolute accuracy ? 0.1 0.25 ? 0.25 0.4 ? 0.4 0.8 %fsr bipolar zero error (tech note 2) ? 0.1 0.15 ? 0.15 0.25 ? 0.25 0.5 %fsr bipolar offset error (tech note 2) ? 0.1 0.2 ? 0.2 0.3 ? 0.3 0.6 %fsr gain error (tech note 2) ? 0.1 0.25 ? 0.25 0.4 ? 0.4 0.9 % no missing codes (f in = 10khz) 18 ?? 18 ?? 18 ?? bits dynamic performance peak harmonics ( ? 0.5db) dc to 100khz ?? 90 ??? 90 ??? 86 ? db 100khz to 500khz ?? 89 ??? 89 ??? 85 ? db total harmonic distortion ( ? 0.5db) dc to 100khz ?? 89 ??? 89 ??? 85 ? db 100khz to 500khz ?? 88 ??? 88 ??? 84 ? db signal-to-noise ratio (w/o distortion, ? 0.5db) dc to 100khz ? 89 ?? 89 ?? 86 ? db 100khz to 500khz ? 88 ?? 88 ?? 85 ? db signal-to-noise ratio ? (& distortion, ? 0.5db) dc to 100khz ? 86 ?? 86 ?? 82 ? db 100khz to 500khz ? 84 ?? 84 ?? 81 ? db noise ? 25 ?? 25 ?? 25 ? vrms two-tone intermodulation distortion (f in = 100khz, 240khz, f s = 1mhz, ? 0.5db) ?? 85 ??? 85 ??? 85 ? db input bandwidth ( ? 3db) small signal ( ? 20db input) ? tbd ?? tbd ?? tbd ? mhz large signal ( ? 0.5db input) ? tbd ?? tbd ?? tbd ? mhz feedthrough rejection (f in = 500khz) ? 84 ?? 84 ?? 84 ? db slew rate ? tbd ?? tbd ?? tbd ? v/s aperture delay time ? +20 ?? +20 ?? +20 ? ns aperture uncertainty ? 5 ?? 5 ?? 5 ? ps rms s/h acquisition time ( to 0.003%fsr, 10v step) ? 260 ?? 260 ?? 260 ? ns overvoltage recovery time ? ? 500 ?? 500 ?? 500 ? ns a/d conversion rate 1 ?? 1 ?? 1 ?? mhz parameters limits units +15v supply (pin 9) 0 to +16 volts ? 15v supply (pin 8) 0 to ? 16 volts +5v supply (pins 10, 14) 0 to +6 volts ? 5v supply (pin 11) 0 to ? 6 volts digital input (pin 16) ? 0.3 to +v dd +0.3 volts analog input (pin 4) 15 volts lead temperature (10 seconds) +300 c parameters min. typ. max. units operating temp. range, case ADS-951MC 0 ? +70 c ads-951mm ? 55 ? +125 c thermal impedance jc ? 5 ? c/watt ca ? 22 ? c/watt storage temperature range ? 65 ? +150 c package type 32-pin,side-brazed, metal-sealed, ceramic tdip weight 0.46 ounces (13 grams) absolute maximum ratings physical/environmental functional specifications (t a = +25 c, v cc = 15v, v dd = 5v, 1mhz sampling rate, and a minimum 1 minute warmup ? unless otherwise specified.)
ads-951 3 ?? +25 c 0 to +70 c ? 55 to +125 c analog output min. typ. max. min. typ. max. min. typ. max. units internal reference voltage +4.95 +5.0 +5.05 +4.95 +5.0 +5.05 +4.95 +5.0 +5.05 volts drift ? 30 ?? 30 ?? 30 ? ppm/ c external current ? 1 ?? 1 ?? 1 ? 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" ??? 4 ??? 4 ?? ? 4ma logic loading "0" ?? +4 ?? +4 ?? +4 ma output coding complementary offset binary power requirements power supply ranges +15v supply +14.5 +15.0 +15.5 +14.5 +15.0 +15.5 +14.5 +15.0 +15.5 volts ? 15v supply ? 14.5 ? 15.0 ? 15.5 ? 14.5 ? 15.0 ? 15.5 ? 14.5 ? 15.0 ? 15.5 volts +5v supply +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 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 ? +29 ?? +29 ?? +29 ? ma ? 15v supply ?? 15 ??? 15 ??? 15 ? ma +5v supply ? +104 ?? +104 ?? +104 ? ma ? 5v supply ?? 54 ??? 54 ??? 54 ? ma power dissipation ? 1.45 1.65 ? 1.45 1.65 ? 1.45 1.65 watts power supply rejection ?? 0.05 ?? 0.05 ?? 0.05 %fsr/%v thermal requirements all datel sampling a/d converters are fully characterized and specified over operating temperature (case) ranges of 0 to +70 c and ? 55 to +125 c. all room-temperature (t a = +25 c) production testing is performed without the use of heat sinks or forced-air cooling. thermal impedance figures for each device are listed in their respective specification tables. these devices do not normally require heat sinks, however, standard precautionary 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 underneath the package. devices should be soldered to boards rather than "socketed", and of course, minimal air flow over the surface can greatly help reduce the package temperature. technical notes 1. obtaining fully specified performance from the ads-951 requires careful attention to pc-card layout and power supply decoupling. the device's analog and digital ground systems are not connected to each other internally. for optimal performance, tie all ground pins (3, 12 and 13) directly to a large analog ground plane beneath the package. bypass all power supplies and the +5v reference output (pin 5) to ground with 10f tantalum capacitors in parallel with 0.1f ceramic capacitors. locate the bypass capacitors as close to the unit as possible. tie a 47f capacitor between compensation (pin 7) and ground. 2. the ads-951 achieves its specified accuracies without the need for external calibration. if required, the device's small initial errors can be reduced to zero using the adjustment circuitry shown in figure 2. when using this circuitry, or any similar offset and gain calibration hardware, make adjust- ments following warmup. to avoid interaction, always adjust offset before gain. float pin 6 if not using gain adjust circuits. footnotes: ? this is the time required before the a/d output data is valid once the analog input is back within the specified range. 6.02 (snr + distortion) ? 1.76 + 20 log full scale amplitude actual input amplitude ? 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. ? contact datel for other input voltage ranges. ? a 1mhz clock with a 500nsec positive pulse width (50% duty cycle) is used for all production testing. any duty cycle may be used as long as a minimum positive pulse width of 20nsec is maintained. for applications requiring lower sampling rates, clock frequencies lower than 1mhz may be used. ? effective bits is equal to: 3. applying a start convert pulse while a conversion is in progress (eoc = logic "1") will initiate a new and probably inaccurate conversion cycle. data for the interrupted and subsequent conversions will be invalid.
ads-951 4 ?? zero/offset adjust procedure 1. apply a train of pulses to the start convert input (pin 16) so that the converter is continuously converting. 2. for bipolar zero/offset adjust, apply ? 19v to the analog input (pin 4). 3. adjust the offset potentiometer until the output code flickers equally between 01 1111 1111 1111 1111 and 10 0000 0000 0000 0000. gain adjust procedure 1. apply ? 4.999943v to the analog input (pin 4). 2. adjust the gain potentiometer until all output bits are 1's and the lsb flickers between 1 and 0. 3. to confirm proper operation of the device, vary the applied input voltage to obtain the output coding listed in table 2. biploar input voltage scale 5v msb lsb +fs ? 1 lsb +4.999962 00 0000 0000 0000 0000 +3/4 fs +3.750000 00 0111 1111 1111 1111 +1/2 fs +2.500000 00 1111 1111 1111 1111 0 +0.000000 01 1111 1111 1111 1111 ? 1/2 fs ? 2.500000 10 1111 1111 1111 1111 ? 3/4 fs ? 3.750000 11 0111 1111 1111 1111 ? fs +1 lsb ? 4.999962 11 1111 1111 1111 1110 ? fs ? 5.000000 11 1111 1111 1111 1111 output coding complementary offset binary table 2. output coding calibration procedure connect the converter per table 1 for the appropriate input voltage range. any offset/gain calibration procedures should not be implemented until the device is fully warmed up. to avoid interaction, adjust offset before gain. the ranges of adjustment for the circuits in figure 2 are guaranteed to compensate for the ads-951'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 is accomplished by connecting led's to the digital outputs and performing adjustments until certain led's "flicker" 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-951, offset adjusting is normally accomplished when the analog input is 0 minus ? lsb ( ? 19v). see table 2 for the proper bipolar output coding. gain adjusting is accomplished when the analog input is at nominal full scale minus 1 ? lsb's ( ? 4.999943v). input voltage zero adjust gain adjust range ( ?? lsb) ( ? fs +1 ? lsb) 5v ? 19v ? 4.999943 table 1. input connections
ads-951 5 ?? figure 3. ads-951 timing diagram figure 2. typical ads-951 connection diagram scale is approximately 50ns per division. start convert internal s/h n n+1 500ns typ. acquisition time 260ns typ. 740ns typ. 5ns typ. eoc 65ns typ. conversion time 730ns typ. output data data n-2 valid 980ns typ. hold data n-1 valid 20ns typ. 20ns invalid data n 3 11 ads-951 10 2 1 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 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 bit 15 bit 16 bit 17 bit 18 (lsb) +5v analog 15 analog ground analog ground digital ground 0.1f 10f 0.1f + 10f +5v ref. out compensation 47f 14 13 5 7 start convert +5v digital gain adjust 6 16 0.1f 10f 12 9 0.1f 10f 8 ++ 0.1f 10f 0.1f 10f + + eoc ? 5v analog +15v ? 15v analog input 4 pin 5 (ads-951) 10k
ads-951 datel makes no representation that the use of its products in the circuits described herein, or the use of other technical info rmation contained herein, will not infringe upon existing or future patent rights. the descriptions contained herein do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. specifications are s ubject to change without notice. the datel logo is a registered datel, inc. trademark. ds-0366p 5/27/99 mechanical dimensions inches (mm) ordering information operating 32-pin model number temp. range package ADS-951MC 0 to +70 c tdip ads-951mm ? 55 to +125 c tdip accessories ads-b951 evaluation board (without ads-951) receptacles for pc board mounting can be ordered through amp, inc., part # 3-331272-8 (component lead socket), 32 required. for availability of mil-std-883 product, contact datel. iso 9001 iso 9001 registered datel, inc. 11 cabot boulevard, mansfield, ma 02048-1151 tel: (508) 339-3000 (800) 233-2765 fax: (508) 339-6356 email: sales@datel.com internet: www.datel.com data sheet fax back: (508) 261-2857 datel (uk) ltd. tadley, england tel: (01256)-880444 datel s.a.r.l. montigny le bretonneux, france tel: 01-34-60-01-01 datel gmbh m nchen, germany tel: 89-544334-0 datel kk tokyo, japan tel: 3-3779-1031, osaka tel: 6-354-2025 ?? ?? 1.62 max. (41.15) 0.92 max. (23.37) 0.018 typ. (0.46) 1.50 typ (38.10) 0.100 typ. (2.54) 0.05 typ. (1.27) 0.175 typ (4.45) 0.05 typ. (1.27) 0.220 typ. (6.86) 0.90 typ. (22.86) 0.010 typ. (0.254) 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 0.05 typ. ( 1.27 ) seating plane
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