GENERAL DESCRIPTION
The AD7785 is a low power, low noise, complete analog front end for high precision measurement applications. The AD7785 contains a low noise 20-bit ∑-Δ ADC with three differential analog inputs. The on-chip, low noise instrumentation amplifier means that signals of small amplitude can be interfaced directly to the ADC. With a gain setting of 64, the rms noise is 40 nV when the update rate equals 4.17 Hz.

FEATURES
   Up to 20 bits effective resolution
   RMS noise
      40 nV @ 4.17 Hz
      85 nV @ 16.7 Hz
   Current: 400 μA typical
   Power-down: 1 μA maximum
   Low noise programmable gain instrumentation amp
   Band gap reference with 4 ppm/°C drift typical
   Update rate: 4.17 Hz to 470 Hz
   3 differential inputs
   Internal clock oscillator
   Simultaneous 50 Hz/60 Hz rejection
   Programmable current sources
   On-chip bias voltage generator
   Burnout currents
   Power supply: 2.7 V to 5.25 V
   –40°C to +105°C temperature range
   Independent interface power supply
   16-lead TSSOP package
   Interface
      3-wire serial
      SPI®, QSPI™, MICROWIRE™, and DSP compatible
      Schmitt trigger on SCLK

APPLICATIONS
   Thermocouple measurements
   RTD measurements
   Thermistor measurements
   Gas analysis