低電壓類比數位轉換器之核心電路設計與應用

摘要　　近年來，由於各種數位攝影機、壓力感測計及以離子感測場效電晶體為基礎之酸鹼度計等可攜式裝置之推出，其可由電池供給電壓操作，使得CMOS技術之感測器變得更有吸引力。然而，適於離子感測場效電晶體為基礎應用之低電壓訊號處理電路未見發展與發表。因此，發展微感測器系統之低電壓核心模組的相關研究變得更重要與更有價值。　　本篇論文的主要目的為詳述應用於電池電源操作之低電壓類比數位轉換器核心電路，提出兩階式架構之類比數位轉換器設計與應用。為方便資料擷取與控制，轉換器支援相容於微電腦之介面。類比數位轉換器之解析度為八位元，工作電壓為1.5V；其關鍵電路方塊包含了電阻鏈、電容陣列、比較器、編碼器、類比多工器與閂鎖器；並採用聯華電子股份有限公司（UMC）0.5μm CMOS 2P2M的製程技術完成晶片之製作；量測結果顯示此轉換器僅耗費300uW之功率，微分非線性誤差-1~+2LSB，積分非線性誤差-3~+0。　　為驗證前述兩階式類比數位轉換器之應用與可行性，結合本研究室已發展之1.5V基底輸入型前置放大器所組成之定電壓定電流讀出電路組態，進行氫離子濃度檢測。實驗結果顯示，本系統於pH2到pH12的緩衝溶液，具有可接受之線性度及0.1pH之準確度。關鍵字：離子感測場效電晶體、低電壓、類比數位轉換器、酸鹼度

關鍵字

離子感測場效電晶體；酸鹼度；低電壓；類比數位轉換器

並列摘要

ABSTRACT 　　Due to a variety of battery-operated or portable device applications such as digital camera, pressure sensor, ISFET-based pH meter, etc., CMOS compatible sensor technology becomes more attractive in recent year. However, the circuitry of low-voltage signal processing in update CMOS technology for ISFET-based applications has not yet been developed and published. Therefore, to develop the low-voltage core modules on micro-sensor system related research become more valuable and important. 　　The major objective of this thesis is to discuss the core integrated circuit on low-voltage analog-to-digital converter for battery-operated applications. Two-step A/D converter is presented in this research. It is supported with microcomputer compatible interface. The resolution of the A/D is 8-bit and operated at 1.5V. Key block diagram of this A/D converter consist resistor string, capacitor array, comparator, encoder, analog multiplexer and latch bank, which has been fabricated in UMC 0.5μm double-poly double-metal CMOS technology. The measured results show that the ADC consumes 300μW only, the INL and DNL are –1~+2LSB and -3~0 respectively. 　　In addition, the mentioned two-step ADC above was integrated with a previous developed 1.5V bulk-driven pre-amplifier for H+ sensing applications. The experimental results show that the proposed circuitry has an acceptable linearity to 0.1pH accuracy with the buffer solution in the range of pH2 to pH12. Keyword: ISFET, low-voltage, analog-to-digital converter, pH

並列關鍵字

analog-to-digital converter ； low-voltage ； pH ； ISFET

參考文獻

[18]王勇順, 生物感測器訊號處理之關鍵積體電路方塊設計, 中原大學碩士論文, June 2002

[19]葉茂祥, 尿素感測器低電壓前置放大器及系統應用之設計研究, 中原大學碩士論文, June 2002

[1]Phillip E. Allen and Douglas R. Holberg “CMOS Analog Circuit Design”, Oxford, 1987

[3]James L. McCreary and Paul R. Grey, “All-MOS Charge Redistribution Analog-to-Digital Conversion Techniques-Part I”, IEEE Journal of Solid-State Circuit, Vol. SC-10, No. 6, pp. 371-379, Dec. 1975

[4]Ricardo E. Suarez, Paul R. Gray, and David A. Hodges, “All-MOS Charge Redistribution Analog-to-Digital Conversion Techniques-Part II”, IEEE Journal of Solid-State Circuit, Vol. SC-10, No. 6, pp. 379-385, Dec. 1975

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低電壓類比數位轉換器之核心電路設計與應用

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