GENERAL DESCRIPTION
The AD7691 is an 18-bit, charge redistribution, successive approximation, analog-to-digital converter (ADC) that operates from a single power supply, VDD, between 2.3 V and 5 V. It contains a low power, high speed, 18-bit sampling ADC with no missing codes, an internal conversion clock, and a versatile serial interface port. On the CNV rising edge, it samples the voltage difference between the IN+ and IN− pins. The voltages on these pins usually swing in opposite phase between 0 V and REF. The reference voltage, REF, is applied externally and can be set up to the supply voltage.

FEATURES
   18-bit resolution with no missing codes
   Throughput: 250 kSPS
   INL: ±0.75 LSB typ, ±1.5 LSB max (±6 ppm of FSR)
   Dynamic range: 102 dB typ @ 250 kSPS
   Oversampled dynamic range: 125 dB @1 kSPS
   Noise-free code resolution: 20 bits @ 1 kSPS
   Effective resolution: 22.7 bits @ 1 kSPS
   SINAD: 101.5 dB typ @ 1 kHz
   THD: −125 dB typ @ 1 kHz
   True differential analog input range: ±VREF
      0 V to VREF with VREF up to VDD on both inputs
   No pipeline delay
   Single-supply 2.3 V to 5 V operation with
      1.8 V/2.5 V/3 V/5 V logic interface
   Serial interface SPI®/QSPI™/MICROWIRE™/DSP compatible
   Daisy-chain multiple ADCs and busy indicator
   Power dissipation
      5 mW @ 5 V/250 kSPS
      50 μW @ 5 V/1 kSPS
   Standby current: 1 nA
   10-lead package: MSOP (MSOP-8 size) and
      3 mm × 3 mm QFN1 (LFCSP) (SOT-23 size)
   Pin-for-pin compatible with the18-bit AD7690 and 16-bit
      AD7693, AD7688, and AD7687

APPLICATIONS
   Battery-powered equipment
   Data acquisitions
   Seismic data acquisition systems
   DVMs
   Instrumentation
   Medical instruments