27.7 A 0.05mm2 1V capacitance-to-digital converter based on period modulation

This paper presents a digitally assisted period modulation (PM)-based capacitance-to-digital converter (CDC) that is >9× smaller than prior CDCs with >10b resolution [1-4], and improves the energy efficiency by >10× compared to previous PM-based CDCs [1]. This is achieved with the help of a piece-wise charge transfer technique that eliminates the need for a large on-chip integration capacitor, a dual-integration-capacitor scheme that reduces the front-end noise contribution, a sampled-biasing technique that reduces the noise of the integration current, and a current-efficient inverter-based design.