An energy-efficient capacitance-controlled oscillator-based sensor interface for MEMS sensors

This paper presents the optimization and implementation of an area- and energy-efficient capacitance-controlled oscillator-based sensor interface, which outputs a period-modulated signal. This time-based output signal can easily be digitized with a reset counter, which benefits from firstorder quantization noise shaping and oversampling. The circuit is prototyped in 130-nm CMOS technology and takes only 0.05 mm². The performance is validated with both an external variable capacitor and a bare-die MEMS capacitive pressure sensor. The chip consumes 371 μW from a 1.2-V supply voltage and achieves 10.5-b resolution with 10-kHz input bandwidth for an input capacitance ranging from 3.7 to 13.7 pF. For both the external capacitor and the MEMS sensor, measurements show an improved energy efficiency compared to prior period modulation-based sensor interfaces.