| Summary: | 碩士 === 國立中正大學 === 電機工程研究所 === 103 === Diabetes is one of the popular chronic diseases in the twenty-first century. Global diabetes population roams up to three hundred eighty two million, and diabetes are ranked as the fourth in the top ten causes of death in Taiwan in 2013. To maintain stable blood glucose, the diabetic patients need the long-term monitoring of their blood glucose. A solution using biomedical chip for glucose monitoring is attractive in recent years. The chip integrates signal processing, sensing, and wireless transmission capabilities in a tiny chip, which make it portable and real-time monitoring.
The principle of the blood test strip is the biomedical reaction between the glucose and the enzyme to produce the oxidation current. The glucose concentration can be known because the current is proportional to the glucose concentration. This thesis proposes a wirelessly-powering current-mode analog-to-digital converter for blood glucose monitoring which is realized in CMOS 0.18um technology. The current-mode ADC is adopted to convert the oxidation current directly. Compared to the voltage-mode ADC, the current-mode ADC doesn’t need a current-to-voltage converter so it has the less induced noise and wide dynamic range. Moreover, the area of the current-mode converter is smaller than voltage mode implementation due to no required capacitor array, so the fabrication cost can be reduced. The proposed system will combine an electronic paper to display the blood value that directly converted by the current-mode ADC. Thus, the successive approximation (SAR) architecture is employed in the analog-to-digital converter for energy efficiency.
The research includes the experiment of the commercial glucose test strip. The current input range of the current-mode ADC is decided in the range of 1~3uA as our design specification according to the experimental results. The post-layout simulation result of the proposed current-mode ADC at a 20 KS/s sample rate can achieve 46.9dB SNDR and 7.5 bit ENOB with a 2KHz input frequency while the voltage supply is 1.3V. The measured result can achieve 26.96dB SNDR and 4.19 bit ENOB with a 1.5 KHz input frequency while the voltage supply is 1.6V.
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