A novel architecture for a Capacitive-to-Digital Converter using time-encoding and noise shaping

This paper presents a Capacitive-to-Digital Converter (CDC) for MEMS sensors using a time-encoding approach. A common CDC needs an intermediate Capacitive-to-Voltage (CV) stage to perform such a conversion. Instead, this architecture directly transforms the sensor capacitor quantity to a digital value. Additionally it is intended to give flexibility at reduced chip area. The proposed solution maps amplitude information into time domain using an integrating Dual-Slope (DS) converter. Furthermore, this CDC employs quantization error noise shaping to reduce measurement time. Both techniques, namely scaling of the CDC resolution and power consumption, will lead to an efficient implementation without extra cost in area. Auto-zeroing further suppresses the offset and low frequency noise of the amplifier. Simulation results show that a realization in digital CMOS technology will be a promising candidate for a scalable CDC for MEMS sensors.