低雜訊電容讀取電路應用於MEMS壓力計元件之研究

A Study of low noise capacitor readout circuit on MEMS-Pressure device

陳楷錫(Kai-Si Chen)

指導教授 ： 黃榮堂

國立臺北科技大學/機電學院/機電整合研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00347

摘要

本論文提出一種利用MEMS壓力計感測元件，將測得之訊號直接傳入相連的CMOS訊號處理單元中，此訊號處理單元可為電容量測單元，因此能夠直接量測、判斷所測得的極微小電容(femto level)訊號變化。後階段可利用MEMS壓力計陣列形式，以提高不同的壓力感測範圍，以發揮電容感測器的辨識能力，實現可穿戴式（Wearable）或植入式(implantable)單晶片（SoC）的目的。
由於MEMS壓力計在感測壓力時，電容訊號變化大部分為1~200fF等級，利用訊號讀取電路做偵測，再利用公式推算出微結構的初始電容值和電容變化值。於電容訊號感測方面，本研究利用積分器將感測電容變化訊號轉換成電壓訊號，再藉由切換電容式電路作為訊號放大及讀出電路。經由全差分設計的結構，提供了一個良好的雜訊抑制能力。放大器偏移電壓可以經由相關雙取樣技術給消除掉。本系統以TSMC 0.35 μm 2P4M製程來設計感測晶片，晶片面積為1.796*1.8142mm,工作電壓採用3.0V，以33kHz作為CMOS開關工作頻率、輸入1 kHz載波測試，可以感測範圍約數十fF~數百fF之電容值。因此本研究系統確實可有效感測到微量電容變化量。

關鍵字

電容感測器 ； CMOS ； 切換電容式電路 ； 積分器

並列摘要

In this thesis, a new type of capacitor sensor composed of pressure and CMOS circuitry is proposed. The capacitor variation can be measured directly by means of the proposed sensing circuit, which is composed of an impedance amplifier and a switched-capacitor amplifier. The goal of the designed sensor is used to detect the pressure of blood vessel. Furthermore, an array-typed MEMS-pressure sensor can be to detect blood vessel pressures in various pressure ranges, and it is desired to become a wearable or an implantable device.
The sensing capacitor range of the proposed sensor is about 1~200 fF. By using readout circuits and comparing the waveforms generator (in sine wave), we can calculate the capacitor variation of MEMS-pressure sensor. As to measurement of capacitor, we chose an integrator to convert the Pressure-Sensor output capacitor into a voltage in this study. The sensing signals are then amplified and readout with switched-capacitor (SC) circuit. According to the simulation, the proposed system is implemented in TSMC 0.35 μm 2P4M technology. The chip area is roughly 1.796*1.814 with power supply of 3.0V. Through simulation, the CMOS switching frequency is 33KHZ as the input signal of 1 kHz sine waves. The proposed structure has a capacitor measuring range from 1 fF to hundreds of fF. This study successfully presents a smart sensor which can detect a very small capacitor variation of MEMS-pressure sensor.

並列關鍵字

Capacitor Sensor ； CMOS ； Switched-Capacitor Circuit ； Integrator

參考文獻

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