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