The Design of Interface Circuits for MEMS Sensors

Abstract

A new energy-efficient dual-slope capacitance-to-digital interface circuit is proposed. The proposed interface circuit is a general purpose interface that can be adapted for multi-sensors IOT applications. This interface utilizes a new iterative charge sharing technique, which can be easily configured for different capacitive sen-sor ranges. The interface employs a switched capacitor circuit followed by a low-power dynamic comparator and a digital controller with a counter to generate the digital out-put, corresponding to the input capacitance of the sensor. The simplicity of the proposed capacitance-to-digital converter(CDC) architecture leads to an energy efficient interface. Detailed analysis of the proposed CDC architecture with emphasis on the linearity, con-version time, and noise are presented and verified by the simulation. The proposed CDC achieves a resolution of 8.4 bit 1.56pJ FOM for a capacitor sensor range of 8pF and a supply voltage of 1.2V in 0.18 m CMOS technology node.