An Energy-Efficient Capacitive Sensor Readout Circuit With Zoomed Time-Domain Quantization

This letter presents a capacitance-to-digital converter (CDC) with an incremental zoom current-controlled oscillator (CCO)-based time-domain $\Delta \Sigma $ modulator (TD- $\Delta \Sigma \text{M}$ ). It supports single-sensor and single-shot measurement, which provides significant power saving. A double-PFD (DPFD) quantizer achieves $2\times $ resolution enhancement compared to conventional PFD. A fast start-up scheme for CCO boosts conversion speed and ensures first conversion accuracy. The proposed design achieves 9.7 fJ/conv.-step with a short measurement time of $4.1~\mu \text{s}$ . To the authors’ best knowledge, it realizes the best energy efficiency and shortest measurement time among all high-resolution CDCs achieving over 12 ENOB.