具溫度補償及直流偏移校正之加速度計讀出電路設計

Abstract

本論文提出可以在混合訊號微機電製程下，完成加速度計及讀出電路設計，此讀出電路具有溫度補償及直流偏移校正之功能。因溫度變異影響加速度計靈敏度及放大器增益，故此溫度補償機制需補償兩種不同之誤差量，為了減少溫度之影響，在讀出電路中加入自動增益控制電路及直流偏移校正電路，使得讀出電路不易受溫度影響。根據美國國防部提出之規範(MIL-PRF-38534)，對於消費性電子產品可以容忍之溫度範圍是攝氏0度至攝氏70度，在此範圍中其工作之特性需盡可能維持一定，本論文提出之架構可容忍之溫度範圍為攝氏-20度至攝氏80度，其溫度造成之靈敏度變異為230 ppm/℃。

A monolithic accelerometer with integrated capacitance to voltage readout circuit as well as temperature compensation and DC-offset cancellation circuit in 0.18μm CMOS MEMS process is proposed in this thesis. Since temperature variation affects the sensitivity of MEMS accelerometer and gain value of the readout circuit, the compensation scheme needs to deal with two kinds of errors. In order to reduce the effect of temperature and make the readout circuit more temperature independent, an automatic-gain control (AGC) circuit and a DC-offset cancellation loop are attached to the readout. According to the specification for United States Department of Defense (MIL-PRF-38534), the tolerance of temperature variation for consumer electronics devices is from 0 ℃ to 70 ℃ and the performances of devices should keep similar in this range. The tolerance of proposed circuit architecture is designed from -20 ℃ to 80 ℃, the sensitivity variation is 230 ppm/℃.