Design and analysis of a first-order sigma-delta converter with CMOS-MEMS differential capacitive sensor

Abstract

This dissertation presents the design and analysis of a MEMS accelerometer and its accompanying interface circuitry. The interface circuit is a sigma-delta (Σ-Δ) analog-to-digital converter (ADC) which is capable of converting an analog low voltage (in mV range) and low frequency signal into digital signals. The first-order 1-bit Σ-Δ ADC is designed and simulated using MATLAB® and CadenceTM Spectre design tools. Σ-Δ converters are preferred for MEMS applications due to its capabilities of processing low output voltages from MEMS sensors and its noise-shaping techniques which push the noise outside the bandwidth of the baseband signals. The MEMS accelerometer is designed as a CMOS-MEMS differential capacitive sensor. The usage of CMOS technology to form the sensor allows integration of the MEMS sensor with its ADC interface circuitry together on the same chip. Each component in the converter is designed and simulated separately using Silterra 0.13um CMOS process technology. Simulation results indicate agreement with the theoretical evaluations.