Analogue, Mixed Signal, LSI


Capacitance-to-digital converters

28 February 2022 Analogue, Mixed Signal, LSI

The AD7745 and AD7746 from Analog Devices are high-resolution Σ-Δ capacitance-to-digital converters. Their architecture features inherently high resolution (24-bit no missing codes, up to 21-bit effective resolution), high linearity (±0,01%) and high accuracy (±4 fF factory calibrated). The capacitance input range is ±4 pF (changing), while it can accept up to 17 pF common-mode capacitance (unchanging), which can be balanced by a programmable on-chip digital-to-capacitance converter.

The AD7745 has one capacitance input channel, while the AD7746 has two channels. Each channel can be configured as single-ended or differential. The AD7745/AD7746 are designed for floating capacitive sensors. For capacitive sensors with one plate connected to ground, the AD7747 is recommended.

The parts have an on-chip temperature sensor with a resolution of 0,1°C and accuracy of ±2°C. The on-chip voltage reference and the on-chip clock generator eliminate the need for any external components in capacitive sensor applications. The parts have a standard voltage input which, together with the differential reference input, allows easy interfacing to an external temperature sensor such as an RTD, thermistor or diode.

For more information contact Conrad Coetzee, Altron Arrow, +27 11 923 9600, [email protected], www.altronarrow.com


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