Design, integration and performance analysis of ΣΔ ADC for capacitive sensor interfacing

Micro-Electro-Mechanical System (MEMS) sensors are integrated with suitable signal conditioning unit (SCU) to provide usable output. Though the output of the SCU can be either analog or digital, digital output is often required in many system applications where other components are mostly digital. This work integrates a sigma-delta (ΣΔ) Analog to Digital Converter (ADC) with an analog front-end for capacitive sensor applications. The ΣΔ ADC is designed and fabricated in UMC 180 nm CMOS process along with the analog front-end. Peak SNR of 40 dB is achieved which corresponds to 7 bits of resolution. The entire system can be used up to 1 kHz signal frequency.