An All-Digital Capacitance-to-Digital Converter Based on Time-to-Digital Converter

This paper presents a capacitive-to-digital converter (CDC) based on a time-to-digital converter (TDC). The proposed three-stage Vernier TDC achieves both high time resolution and wide time conversion range. In comparison to alternative CDC implementations, the proposed TDC is wholly digital, which results in reduced power consumption and more straightforward integration with other digital circuits within the system. The proposed CDC was implemented in a standard 0.18 μm CMOS process and demonstrated a capacitance conversion range of 150 pF to 700 pF and TDC with a time resolution of 14 ps. These results indicate that this capacitive digital converter is suitable for sensor applications and other systems requiring high conversion resolution.