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 M). It supports single-sensor and single-shot measurement, which provides significant power saving. A double-PFD (DPFD) quantizer achieves 2x 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 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.