A 117-dB In-Band CMRR 98.5-dB SNR Capacitance-to-Digital Converter for Sub-nm Displacement Sensing with an Electrically Floating Target

Abstract

This article describes a high-performance capacitance-to-digital converter (CDC) for sub-nm displacement sensing with an electrically floating target. Intended to be integrated into a displacement sensor probe, the CDC consumes only 560μW. It achieves 98.5-dB SNR in a 1-ms conversion time. With a sensing O 8-mm probe and a 25μm stand-off distance from the target, it achieves 0.18-nm resolution. Moreover, it offers an in-band common-mode rejection ratio (CMRR) higher than 117 dB, providing decent electric field interference immunity.