A 9.7fJ/Conv.-Step Capacitive Sensor Readout Circuit with Incremental Zoomed Time Domain Quantization

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This paper presents a capacitive sensor readout circuit with an incremental zoom current-controlled oscillator (CCO)-based timedomain (TD) ΔΣM. It supports single-sensor measurement, leading to 2x savings in sensing hardware compared to dual-sensor schemes. A low-cost 5b TD-ΔΣM is implemented with a 7- stage ring-CCO and a double-PFD (DPFD) quantizer. To further boost its speed, a fast start-up scheme is designed for the CCO quantizer. Combining all these merits, the proposed readout circuit achieves 0.23fF resolution while dissipating only 61pJ per conversion with a short measurement time of 4.1μs. To the authors’ best knowledge, it realizes the best energy efficiency and shortest measurement time among all high-resolution capacitanceto-digital converters (CDCs) achieving over 12 ENOB.


Zilong Shen (Peking University)
Xiyuan Tang (Peking University)
Zhongyi Wu (Peking University)
Haoyang Luo (Peking University)
Zongnan Wang (Peking University)
Xing Zhang (Peking University)
Yuan Wang (Peking University)

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