使用SAR系統回授感測酸鹼度之機制

Abstract

本論文提出一個使用SAR系統回授感測酸鹼度的電路架構。此系統包含一個前端感測電路與10位元連續近似式數位類比轉換器(DAC)。將酸鹼感測器放入DAC的系統中形成一個SAR ADC封閉迴路，以達到降低製作成本以及較低硬體數量實現整個酸鹼感測類比數位轉換器。作為一個酸鹼離子感測器，在積體電路設計方面主要以離子感測場效電晶體(ISFET)與ISFET元件之延伸式離子感測場效電晶體(EGFET)感測水中氫離子濃度為主。基於本論文主要為電路設計，故採用EGFET以結合國家晶片系統設計中心(CIC)的UMC 0.18um標準CMOS製程下完成，並實現具SAR系統回授感測酸鹼度的單一晶片。 本論文利用EGFET進行酸鹼度感測，並將感測器與前端電路置入DAC封閉迴路中實現一10位元連續近似式類比數位轉換器(SAR ADC)，將pH值做數位訊號輸出。其中供應電壓為1.8V，操作頻率為100kHz，晶片佈局面積為1.415mm x 0.915mm ，酸鹼值量測範圍為pH 2.00~pH 12.00，量測解析度為0.01pH ，整體功耗為285uW。

The thesis proposes a system architecture that uses a SAR system feedback for sensing pH value. The system includes a front-end sensing circuit with a 10-bit Digital-Analog Converter (DAC). The proposed is to place the pH sensor in the system loop to form a SAR ADC. It achieves lower production cost and lower hardware overhead. As a pH sensor, it mainly senses the concentration of hydrogen ions in water by Ion-Sensitive Field-Transistor (ISFET) element and Extended-Gate of ISFET (EGFET) in the integrated circuit design. Due to ISFET components require special manufacturing process and post process, we use EGFET fabricated with CIC UMC 0.18um standard CMOS process to complete the single chip pH sensing with SAR feedback system. The thesis uses EGFET to sense pH and put the sensor and the front-end circuit in the closed loop of a 10-bit SAR ADC. In this system, the power supply voltage is 1.8V, and the clock frequency is 100kHz. The area of chip is 1.415mm x 0.915mm. The sensing range is from pH 2.00 to pH 12.00, and the resolution is 0.01pH . The total power consumption is 285uW.