A 2.69uW Dual Quantization-based Capacitance-to-Digital Converter for Pressure, Humidity, and Acceleration Sensing in 0.18um CMOS

Abstract

This paper presents pressure, humidity, and acceleration sensor in standard CMOS process equipped with an energy-efficient capacitance-to-digital converter (CDC). Air pressure and humidity are sensed using interdigitated top metal that exhibits change in dielectric constant in air and polyimide, respectively. Acceleration is sensed by detecting the differential change in separation among bondwires. Capacitance change induced by transducers is quantized by using a capacitance-to-digital converter (CDC) based on a dual quantization architecture that employs a single-bit 1st-order ΔΣ modulator and a 7-bit SAR ADC. The CDC handles up to 18.2pF and achieves 296aF resolution while consuming 2.69uW. Pressure, humidity, and acceleration sensors achieve a resolution of 0.08psi/√Hz, 0.0014%RH/√Hz, and 4.6mg/√Hz, respectively.