GENERAL DESCRIPTION
The AD7631 is an 18-bit, charge redistribution, successive approximation register (SAR), architecture analog-to-digital converter (ADC) fabricated on Analog Devices, Inc.’s iCMOS high voltage process. The device is configured through hardware or via a dedicated write-only serial configuration port for input range and operating mode. The AD7631 contains a high speed 18-bit sampling ADC, an internal conversion clock, an internal reference (and buffer), error correction circuits, and both serial and parallel system interface ports. A falling edge on CNVST samples the fully differential analog inputs on IN+ and IN−. The AD7631 features four different analog input ranges. Power is scaled linearly with throughput. Operation is specified from −40°C to +85°C.

FEATURES
   Multiple pins/software-programmable input ranges
      +5 V (10 V p-p), +10 V (20 V p-p), ±5 V (20 V p-p),
         ±10 V (40 V p-p)
   Pins or serial SPI-compatible input ranges/mode selection
   Throughput: 250 kSPS
   INL: ±1.5 LSB typical, ±2.5 LSB maximum (±9.5 ppm of FSR)
   18-bit resolution with no missing codes
   Dynamic range: 102.5 dB
   SNR: 101 dB @ 2 kHz
   THD: −112 dB @ 2 kHz
   iCMOS® process technology
   5 V internal reference: typical drift 3 ppm/°C; TEMP output
   No pipeline delay (SAR architecture)
   Parallel (18-/16-/8-bit bus) and serial 5 V/3.3 V interface
   SPI-/QSPI™-/MICROWIRE™-/DSP-compatible
   Power dissipation
      73 mW @ 250 kSPS
      10 mW @ 1 kSPS
   Pb-free, 48-lead LQFP and 48-lead LFCSP (7 mm × 7 mm)

APPLICATIONS
   Process controls
   High speed data acquisition
   Digital signal processing
   Spectrum analysis
   ATE