應用於生醫之低功率無線電化學感測積體電路

Abstract

近年來，隨著人口高齡化以及少子化的趨勢，醫療人員不足的問題逐漸擴大。為了解決醫療人員不足的問題，無線健康照護系統的概念被提出。利用攜帶型或植入型裝置，提供了個人化且即時的健康資訊檢測，再透過雲端系統將資訊彙整給醫護人員，大大降低了所需專業人力成本。對於無線健康檢測系統，為了方便攜帶或植入並提供長時間檢測，面積及功率消耗為重要的設計考量。 本論文實現了一個無輸出電容之低功率與低壓降穩壓器以及一個低功率電化學的無線感測系統。在穩壓器的部分，利用反轉式電壓追隨器的架構並整合了帶差參考電路，移除了傳統架構上所需之運算放大器的使用以及大輸出電容的需求，實現了低功率小面積的電路需求。此次設計穩壓器之溫度系數在0-100oC為68ppm/oC，PSR為-50dB，靜態電流消耗為4.5µA，電路面積為0.076mm2。而在無線電化學感測系統上，利用RF無線能量擷取及注入式鎖定的技巧取代了傳統上所需之電池及石英振盪器。在電路設計上，提出了一個新型的全CMOS電壓參考電路，並將感測信號以時間量化取代傳統上電壓量化的操作，大大減少了被動元件的使用，同時，利用背向散射的傳輸機制，解決了主動傳輸所需之大量的能量消耗，並利用調變頻率注入鎖定的技巧降低振盪器之操作頻率，使整體系統達到低功率小面積的需求。此次提出之系統達到289Hz/nA感測靈敏度以及R2為0.997之線性度。整體系統僅消耗2.2 µW並可以在-12 dBm的無線能量下進行操作，晶片面積為1 mm2。此論文設計晶片皆使用台積電0.18 µm製程。

Nowadays, the shortage of healthcare manpower becomes a serious problem due to the aging society and low birth rate. To solve the problem, the concept of wireless healthcare system is proposed. Implantable or portable monitoring system provides a personal health care and fast alarm by the cloud network to save professional manpower. The power consumption and chip’s area are two critical issues in portable or implantable healthcare system in order to function continuously within a limited area. In this thesis, an output capacitor-less flipped voltage follower low dropout regulator and a low power wireless electrochemical sensing system are proposed. The proposed regulator removes the bulky output capacitor and the operational amplifier in conventional low dropout regulator design by flipped voltage follower technique with embedded bandgap reference. The proposed regulator achieves temperature coefficient 68ppm/oC over 0-100 oC with a PSR of -50dB. The quiescent current is 4.5 µA and the active area is 0.076mm2. In wireless sensing system design, RF power and injection locking technique are adopted to avoid the bulky batteries and crystal resonators. In circuit design, an all CMOS voltage reference generator is proposed, and the time operation of sensing signal alternates the conventional voltage operation. Besides, the backscattering and envelope injection techniques solve the issue of large power consumption in wireless transmission and high frequency injection locking oscillator. The proposed system achieves a sensitivity of 289 Hz/nA and an R2 linearity of 0.997, and consumes 2.2 µW and can be powered by -12 dBm RF power with 1mm2 chip’s area. The proposed low-power techniques with no external components can be widely used in biomedical systems for disease diagnosis and biomarker analysis.