AD783–SPECIFICATIONS DC SPECIFICATIONS (TMIN to TMAX with VCC = +5 V 6 5%, VEE = –5 V 6 5%, CL = pF, unless otherwise noted) Parameter Min SAMPLING CHARACTERISTICS Acquisition Time 5 V Step to 0.01% 5 V Step to 0.1% Small Signal Bandwidth Full Power Bandwidth HOLD CHARACTERISTICS Effective Aperture Delay (+25°C) Aperture Jitter (+25°C) Hold Settling (to 1 mV, +25°C) Droop Rate Feedthrough (+25°C) (VIN = ± 2.5 V, 500 kHz) –30 AD783J/A Typ Max Units 250 200 15 2 375 350 ns ns MHz MHz 15 20 150 0.
AD783 HOLD MODE AC SPECIFICATIONS (T MIN to TMAX with VCC = +5 V 6 5%, VEE = –5 V 6 5%, CL = 50 pF, unless Parameter AD783J/A Typ Min otherwise noted) Max Units –80 dB dB TOTAL HARMONIC DISTORTION fIN = 100 kHz fIN = 500 kHz –85 –72 SIGNAL-TO-NOISE AND DISTORTION fIN = 100 kHz fIN = 500 kHz 77 70 dB dB INTERMODULATION DISTORTION (F1 = 99 kHz, F2 = 100 kHz) Second Order Products Third Order Products –80 –85 dB dB NOTES 1 fIN amplitude = 0 dB and f SAMPLE = 300 kHz unless otherwise indicated
AD783–Typical Characteristics 10.0 V+ 60 V– DROOP RATE – µV/µs 1.0 PSRR – dB 50 40 0.1 0.01 30 0.001 0 1 10 100 1k 10k 100k 0 1M 25 50 75 100 TEMPERATURE – °C FREQUENCY – Hz Power Supply Rejection Ratio vs. Frequency 125 150 Droop Rate vs. Temperature, VIN = 0 V 200 ACQUISITION TIME – ns 150 BIAS CURRENT – nA 100 50 0 –50 –100 300 250 200 –150 0 –200 –2.5 0 INPUT VOLTAGE – V 0 +2.5 1 2 3 INPUT STEP – V 4 5 Acquisition Time (to 0.01%) vs.
AD783 Output Drive Current—The maximum current the SHA can source (or sink) while maintaining a change in hold mode offset of less than 2.5 mV. DEFINITIONS OF SPECIFICATIONS Acquisition Time—The length of time that the SHA must remain in the sample mode in order to acquire a full-scale input step to a given level of accuracy.
AD783 DYNAMIC PERFORMANCE (VOUT HOLD – VIN ), mV VOUT ACQUISITION ACCURACY – % The AD783 is compatible with 12-bit A-to-D converters in terms of both accuracy and speed. The fast acquisition time, fast hold settling time and good output drive capability allow the AD783 to be used with high speed, high resolution A-to-D converters like the AD671 and AD7586. The AD783’s fast acquisition time provides high throughput rates for multichannel data acquisition systems.
AD783 The accuracy in sampling high frequency signals is also constrained by the distortion and noise created by the sample-and-hold. The level of distortion increases with frequency and reduces the “effective number of bits” of the conversion. The AD783 does not provide separate analog and digital ground leads as is the case with most A-to-D converters. The common pin is the single ground terminal for the device.
AD783 TO AD670 INTERFACE The 15 MHz small signal bandwidth of the AD783 makes it a good choice for undersampling applications. Figure 8 shows the interface between the AD783 and the AD670 ADC, where the AD783 samples the incoming IF signal. For this particular application, the IF carrier was 10.7 MHz and the information signal was a 5 kHz FSK-modulated tone. The sample-and-hold signal is applied to the 8-bit AD670 ADC and then digitally processed for analysis.
