GENERAL DESCRIPTION

The AD7747 is a high-resolution, Σ-Δ 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 19.5-bit effective resolution), high linearity (±0.01%), and high accuracy (±10 fF factory calibrated). The AD7747 capacitance input range is ±8 pF (changing), and it can accept up to 17 pF common-mode 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 20 aF (that is, up to 19.5-bit ENOB)
Accuracy: 10 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
0.7 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
Flow metering
Impurity detection