? ? ads-942 14-bit, 2mhz sampling a/d converters fea tures 14-bit resolution 2mhz minimum throughput functionally complete internal reference and sample/hold -85db total harmonic distortion 78db signal-to-noise ratio full nyquist-rate sampling small 32-pin dip low-power, 2.9 watts general description datel's ads-942 is a functionally complete, 14-bit, 2mhz, sampling a/d converter. its standard, 32-pin, triple-wide ceramic dip contains a fast-settling sample/hold amplifier, a 14-bit subranging (two-pass) a/d converter, a precision reference, three-state output register and all the timing and control logic necessary to operate from a single start convert pulse. the ads-942 is optimized for wideband frequency-domain applications and is fully fft tested. the ads-942 requires 15v and +5v supplies and typically consumes 2.9 watts. input/output connections 1 +10v ref . out 32 st ar t conver t 2 bipolar 31 bit 1 out (msb) 3 analog input 30 bit 1 out (msb) 4 signal gr ound 29 bit 2 out 5 offset adjust 28 bit 3 out 6 analog gr ound 27 bit 4 out 7 o verflo w 26 bit 5 out 8 coding select 25 bit 6 out 9 enable 24 bit 7 out 10 +5v suppl y 23 bit 8 out 11 digit al gr ound 22 bit 9 out 12 +15v suppl y 21 bit 10 out 13 ?15v suppl y 20 bit 11 out 14 analog gr ound 19 bit 12 out 15 analog gr ound 18 bit 13 out 16 eoc 17 bit 14 out (lsb) pin function pin function figure 1. ads-942 functional block diagram ref r e g i s t e r r e g i s t e r 31 bit 1 out (msb) 30 bit 1 out (msb) 29 bit 2 out 28 bit 3 out 27 bit 4 out 26 bit 5 out 25 bit 6 out 24 bit 7 out 23 bit 8 out 22 bit 9 out 21 bit 10 out 20 bit 11 out 19 bit 12 out 18 bit 13 out 17 bit 14 out (lsb) timing and control logic +10v ref. out 1 start convert 32 eoc 16 d i g i t a l c o r r e c t i o n l o g i c dac flash adc buffer analog input 3 s 2 s 1 4 signal ground 11 digital ground 12 +15v supply 3 - s t a t e o u t p u t r e g i s t e r s/h offset circuit bipolar 2 offset adjust 5 10 +5v supply 6, 14, 15 analog ground 8 coding select 13 ?15v supply 9 enable 7 overflow datel, inc., 11 cabot boulevard, mansfield, ma 02048-1151 ( u .s .a .) tel: (508) 339-3000 fax: (508) 339-6356 for immediate assistance: (800) 233-2765
? ? ads-942 2 functional specifica tions (t a = +25c, v cc = 15v, +v dd = +5v, 2mhz sampling rate, and a minimum 7 minute warmup unless otherwise specified.) analog inputs min. typ. max. units input voltage range unipolar ? 0 to +10 ? volts bipolar ? 5 ? volts input impedence 4.9 5 ? k w input capacitance ? 7 15 pf digital inputs logic levels logic "1" +2.0 ? ? volts logic "0" ? ? +0.8 volts logic loading "1" ? ? +5 a logic loading "0" ? ? ?600 a performance integral non-linearity (f in = 1mhz) +25c ? 1 2 lsb 0 to +70c ? 1 2 lsb ?40 to +85c ? 2 3 lsb differential non-linearity (f in = 1mhz) +25c ?0.75 0.5 0.75 lsb 0 to +70c ?0.95 0.75 1.25 lsb ?40 to +85c ?1 1 +2.5 lsb full scale absolute accuracy +25c ? 0.1 0.122 %fsr 0 to +70c ? 0.12 0.36 %fsr ?40 to +85c ? 0.45 0.85 %fsr unipolar zero error +25c (see figure 3) ? 0.05 0.122 %fsr 0 to +70c ? 0.1 0.2 %fsr ?40 to +85c ? 0.2 0.3 %fsr bipolar zero error +25c (see figure 3) ? 0.05 0.122 %fsr 0 to +70c ? 0.1 0.2 %fsr ?40 to +85c ? 0.2 0.3 %fsr bipolar offset error +25c (see figure 3) ? 0.1 0.2 %fsr 0 to +70c ? 0.12 0.3 %fsr ?40 to +85c ? 0.5 0.8 %fsr gain error +25c (see figure 3) ? 0.018 0.122 % 0 to +70c ? 0.12 0.3 % ?40 to +85c ? 0.6 0.8 % no missing codes (f in = 500khz) 14 bits 0 to +70c 13 bits ?40 to +85c resolution 14 bits outputs min. typ. max. units output coding staight bin./offset bin./2's comp. comp. bin./comp. offset bin./c2c logic level logic "1" +2.4 ? ? volts logic "0" ? ? +0.4 volts logic loading "1" ? ? ?160 a logic loading "0" ? ? +6.4 ma internal reference voltage, +25c +9.98 +10.0 +10.02 volts drift ? 13 30 ppm/c external current ? ? 5 ma dynamic performance total harm. distort. (?0.5db) dc to 100khz ? ?85 ?76 db 100khz to 500khz ? ?80 ?75 db 500khz to 1mhz ? ?77 ? db signal-to-noise ratio (w/o distortion, ?0.5db dc to 100khz 74 78 ? db 100khz to 500khz 73 75 ? db 500khz to 1mhz ? 73 ? db signal-to-noise ratio (and distortion, ?0.5db) dc to 100khz 73 78 ? db 100khz to 500khz 72 75 ? db 500khz to 1mhz ? 72 ? db spurious free dyn. range dc to 100khz ? ?86 ?77 db 100 to 500khz ? ?81 ?75 db 500khz to 1mhz ? ?78 ? db two-tone imd distortion (f in = 100khz, 240khz, fs = 2.0mhz, ?0.5db) ?85 ? ? db input bandwidth (?3db) small signal (?20db input) ? 6 ? mhz large signal (?0.5db input) ? 1.75 ? mhz slew rate ? 250 ? v/s aperture delay time ? ? 10 ns aperature uncertainty ? ? 5 ps, ms s/h acq. time , (to 0.003%fsr) sinusoidal (f in = 1mhz) ? 120 150 ns step input ? 250 450 ns conversion rate sinusoidal (f in = 1mhz) 2 ? ? mhz step input 1.3 ? ? mhz feedthrough rejection (f in = 1mhz) ? 85 ? db overvoltage recovery, 12v ? 1000 2000 ns noise ? 250 ? vrms power requirements power supply ranges +15v supply +14.25 +15.0 +15.75 volts ?15v supply ?14.25 ?15.0 ?15.75 volts +5v supply +4.75 +5.0 +5.25 volts power supply currents +15v supply ? +65 +87 ma ?15v supply ? ?80 ?98 ma +5v supply ? +150 +165 ma power dissipation ? 2.9 3.4 watts power supply rejection ? ? 0.02 %fsr%v physical/environmental operating temp. range, case ADS-942MC 0 ? +70 c ads-942me ?40 ? +85 c storage temperature range ?65 ? +150 c package type 32-pin, metal-sealed, ceramic tdip weight 0.46 ounces (13 grams) absolute maximum ra tings p arameters limits units +15v supply (pin 12) 0 to +16 volts ?15v supply (pin 13) 0 to ?16 volts +5v supply (pin 10) 0 to +6 volts digital inputs (pin 8,9, 32) ?0.3 to +v dd +0.3 volts analog input (pin 3) 15 volts lead temp. (10 seconds) +300 c footnote: same specification as in-band harmonics and peak harmonics.
? ? ads-942 3 for unipolar, adjust the zero trimpot so that the output code flickers equally between 00 0000 0000 0000 and 00 0000 0000 0001 with coding select (pin 8) tied low (straight binary) or between 11 1111 1111 1111 and 11 1111 1111 1110 with pin 8 tied high (complementary binary). for bipolar operation, adjust the trimpot until the code flickers equally between 10 0000 0000 0000 and 10 0000 0000 0001 with pin 8 tied low (offset binary) or between 01 1111 1111 1111 and 01 1111 1111 1110 with pin 8 tied high (complementary offset binary). two's complement coding requires using bit 1 out (msb) (pin 31). with pin 8 tied low, adjust the trimpot until the code flickers between 00 0000 0000 0000 and 00 0000 0000 0001. 3. full-scale adjustment set the output of the voltage reference used in step 2 to the value shown in table 2. table 2. zero and gain adjustments input zero adjust gain adjust range +1/2 lsb fs ? 1? lsb 0 to +10v +305v +9.999085v 5v +305v +4.999085v adjust the gain trimpot until the output code flickers equally between 11 1111 1111 1110 and 11 1111 1111 1111 with pin 8 tied low for straight binary/offset binary or between 00 0000 0000 0000 and 00 0000 0000 0001 with pin 8 tied high for complementary binary/complementary offset binary. two?s complement coding requires using pin 31. with pin 8 tied low, adjust the gain trimpot until the output code flickers equally between 01 1111 1111 1110 and 01 1111 1111 1111. 4. to confirm proper operation of the device, vary the precision reference voltage source to obtain the output coding listed in table 3. technical no tes 1. rated performance requires using good high-frequency circuit board layout techniques. connect the digital and analog grounds to one point, the analog ground plane beneath the converter. due to the inductance and resis- tance of the power supply return paths, return the analog and digital ground separately to the power supplies. signal ground (pin 4) is not internally connected to analog ground (pins 6, 15). 2. bypass the analog and digital supplies and the +10v ref. out (pin 1) to ground with a 4.7f, 25v tantalum electro- lytic capacitor in parallel with a 0.1f ceramic capacitor. 3. coding select(pin 8) is compatible with cmos/ttl logic levels for those users desiring logic control of this function. there is an internal pull-up resistor on this pin; connect to +5v or leave open for logic 1. see the calibra- tion procedure for selecting an output coding. 4. to enable the three-state outputs, connect enable (pin 9) to a logic "0" (low). to disable, connect pin 9 to a logic "1" (high). figure 2. ads-942 timing diagram input range input pin tie together 0 +10v pin 3 pins 2 and 4 5v pin 3 pins 1 and 2 table 1. input connections calibra tion pr ocedure 1. connect the converter per figure 3 and table 1 for the appropriate input voltage range. apply a pulse of 35 nanoseconds minimum to start convert (pin 32) at a rate of 200khz. this rate is chosen to reduce flicker if led's are used on the outputs for calibration purposes. 2. zero adjustments apply a precision voltage reference source between analog input (pin 3) and signal ground (pin 4), then adjust the reference source output per table 2. note: scale is approximately 25ns per division. start convert internal s/h n n+1 35ns max.. eoc 10ns typ. 15ns max. output data data n valid 300ns min. hold data n-1 valid 30ns max. 35ns min., 50ns typ., 60 ns max 35ns typ. 350ns min. 150ns max. aquisition time invalid data 200ns max. conversion time 300ns typ., 325ns max.
? ? ads-942 4 removing system errors use external potentiometers to remove system errors or to reduce the small initial errors to zero. use a 100 w trimpot in series with the analog input for gain adjustment. use a fixed 50 w resistor instead of the trimpot for operation without adjustment. use a 20k w trimpot with the wiper tied to offset adjust (pin 5) for zero/offset adjustment. connect pin 5 to analog ground (pin 6) for operation without zero/offset adjustment. figure 3. ads-942 connection diagram ads-942 20k w 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 7 16 bit 1 out (msb) bit 1 out (msb) bit 2 out bit 3 out bit 4 out bit 5 out bit 6 out bit 7 out bit 8 out bit 9 out bit 10 out bit 11 out bit 12 out bit 13 out bit 14 out (lsb) overflow eoc analog ground digital ground 0.1f 4.7f 0.1f enable 4.7f +10v ref. out coding select 10 11 9 1 8 +5v ?15v +15v offset adjust 5 3 0.1f 4.7f 6, 14, 15 13 0.1f 4.7f 12 + + ?15v +15v 32 start convert analog input 100 w 2 bipolar 4 signal ground zero/offset adjust 0 to +10v gain adjust +5v table 3. output coding unipolar input v ol t . output coding input v ol t . bipolar scale 0 t o +10v msb lsb msb lsb msb lsb 5v scale +fs ? 1 lsb +9.999390 11 11 1 1 1111 1111 00 0000 0000 0000 01 1111 1111 1111 +4.999390 +fs ? 1lsb +7/8 fs +8.750000 11 1000 0000 0000 00 0111 1111 1111 01 1000 0000 0000 +3.750000 +3/4fs +3/4 fs +7.500000 11 0000 0000 0000 00 1111 1111 1111 01 0000 0000 0000 +2.500000 +1/2fs +1/2 fs +5.000000 10 0000 0000 0000 01 1111 1111 1111 00 0000 0000 0000 0.000000 0 +1/4 fs +2.500000 01 0000 0000 0000 10 1111 1111 1111 11 0000 0000 0000 ?2.500000 ?1/2fs +1/8 fs +1.250000 00 1000 0000 0000 11 0111 1111 1111 10 1000 0000 0000 ?3.750000 ?3/4fs +1 lsb +0.000610 00 0000 0000 0001 11 1111 1111 1110 10 0000 0000 0001 ?4.999390 ?fs+1lsb 0 0.000000 00 0000 0000 0000 11 1111 1111 1111 10 0000 0000 0000 ?5.000000 ?fs straight bin. comp . binar y off . binar y comp . off . bin. tw o's comp .
? ? ads-942 5 thermal req uirements all datel sampling a/d converters are fully characterized and specified over operating temperature (case) ranges of 0 to +70c and ?55 to +125c. all room-temperature (t a = +25c) 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. in more severe ambient conditions, the package/junction temperature of a given device can be reduced dramatically (typically 35%) by using one of datel's hs series heat sinks. see ordering information for the assigned part number. see page 1-183 of the datel data acquisition components catalog for more information on the hs series. request datel application note an-8, "heat sinks for dip data converters", or contact datel directly, for additional information. figure 4. fft analysis of ads-942 0 ?10 ?20 ?30 ?40 ?50 ?60 ?70 ?80 ?90 ?100 ?110 ?120 ?130 ?140 ?150 frequency (mhz) (fs = 2mhz, fin = 490khz, vin = ?0.5db, 16,384-point fft) a m p l i t u d e r e l a t i v e t o f u l l s c a l e ( d b ) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
? ? ads-942 ? ? datel 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 herein do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. specifications are subject to change without notice. the datel logo is a registered datel, inc. trademark. ds-0228b 10/96 model number operating temp. range ADS-942MC 0 to +70c ads-942me ?40 to +85c accessories ads-eval4 evaluation board (without ads-942) hs-32 heat sink for all ads-942 models ordering informa tion receptacles for pc mounting can be ordered through amp inc., part # 3-331272-8 (component lead socket), 32 required. mechanical dimensions inches (mm) 0.040 (1.016) seating plane 0.025 (0.635) 0.200 max. (5.080) 0.235 max. (5.969) 0.190 max. (4.826) 0.900 0.010 (22.860) 1.11 max. (28.19) 0.100 typ. (2.540) 1.72 max. (43.69) 1 16 17 32 1.500 (38.100) 0.100 (2.540) 0.100 (2.540) 0.018 0.002 (0.457) 0.010 (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 +0.002 ?0.001 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 internet: www.datel.com e-mail:sales@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: 1-34-60-01-01 datel gmbh mnchen, germany tel: 89-544334-0 datel kk tokyo, japan tel: 3-3779-1031, osaka tel: 6-354-2025
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