GENERAL DESCRIPTION
The AD7747 is a high-resolution, Σ−∆ capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device inputs. The architecture features inherent high resolution (24-bit no missing codes, up to 18 bit effective resolution), high linearity (±0.01%), and high accuracy (±8 fF factory calibrated). The AD7747 capacitance input range is ±8 pF (changing), while it can accept up to 17 pF commonmode capacitance (not changing), which can be balanced by a programmable on-chip digital-to-capacitance converter (CAPDAC).

FEATURES
   Capacitance-to-digital converter
      New standard in single chip solutions
      Interfaces to single or differential grounded sensors
      Resolution down to 40 aF (that is, up to 18.5-bit ENOB)
      Accuracy: 8 fF
      Linearity: 0.01%
      Common-mode (not changing) capacitance up to 17 pF
      Full scale (changing) capacitance range ±8 pF
      Update rate: 5 Hz to 45 Hz
      Simultaneous 50 Hz and 60 Hz rejection at 8.1 Hz update
      Active shield for shielding sensor connection
   Temperature sensor on-chip
      Resolution: 0.1°C, accuracy: ±2°C
   Voltage input channel
   Internal clock oscillator
   2-wire serial interface (I2C®-compatible)
   Power
      2.7 V to 5.25 V single-supply operation
      1 mA current consumption
   Operating temperature: –40°C to +125°C
   16-lead TSSOP package

APPLICATIONS
   Automotive, industrial, and medical systems for
      Pressure measurement
      Position sensing
      Proximity sensing
      Level sensing
      Flowmeters
      Impurity detection