舒緩胃食道逆流症狀的 植入式無線供電刺激器晶片設計

Abstract

現在人生活忙碌且飲食習慣不正常，也經常喝咖啡或碳酸性的飲料，這些因素都會導致胃食道逆流(gastroesophageal reflux disease，GERD)的症狀發生，然而傳統的藥物性治療方式僅能夠舒緩胃液分泌，使胃酸逆流症狀緩和而已，對於真正造成胃酸逆流的原因─賁門鬆弛卻沒有治療效果，此外，長期服用藥物的來抑制胃酸分泌也會產生腹痛、腹瀉、頭痛、消化不良、食慾差等副作用。 本論文實做出一個應用導向積體電路(application-specific integrated circuits，ASIC)，該晶片可以植入人體胃壁，其內建的電流刺激器能夠產生電流對食道下端括約肌進行刺激，因此能夠有效改善賁門鬆弛的現象。該電流刺激器可進行低、中、高三種級別的刺激，此三個級別由外部所給定的信號頻率決定，1.3 MHz、1.32 MHz與1.34 MHz的輸入訊號頻率分別對應低、中、高三種刺激級別。此植入式晶片透過無線功率傳輸的方式供電，晶片中內建負載調變機制能夠讓接收端的資料回傳到傳送端。傳送端電路包含了E類放大器與解調變電路，其中E類放大器產生足夠大功率輸出，使得接收端電路能夠穩定運作。解調變電路用來將接收端回傳的資料給還原。 此植入式晶片採用TSMC 0.35um 2P4M CMOS製程實現，整體的晶片面積為0.865*0.904mm2。在傳輸距離為5公分時，植入式晶片的總功率消耗為27.8 mW，E類放大器的功率消耗為508 mW，無線傳輸效率為5.5 %。

Gastro-esophageal reflux disease (GERD) is one of the most common diseases that people nowadays suffer from. Irregular dietary habits, drinking too much caffeinated beverages, and being under high pressure are the main reasons that cause GERD. However, conventional medical treatments for GERD can only ease the symptoms but are not able to address the main cause of GERD. Furthermore, long-term medical treatments for GERD would probably lead to some side effects such as stomachaches, diarrhea, headaches, dyspepsia, and anorexia. An integrated circuit (IC) design of an implantable stimulator is proposed for GERD treatments in this thesis. By implanting the stimulator in the stomach of a GERD patient, the stimulator can generate proper currents to stimulate the lower esophageal sphincter (LES). Once the LES is electrically stimulated, it shrinks and thus blocks up the acid reflux. Therefore, GERD is effectively prevented. The stimulator generates current pulses with three different stimulating intervals according to the frequency of an input signal. The frequencies of 1.30 MHz, 1.32 MHz, and 1.34 MHz correspond to the stimulating intervals of short, middle, and long levels. The implanted stimulator is wirelessly powered and adopts the load-shift keying (LSK) modulation to transmit the sensed data back to the host. As a result, an off-chip transmitter containing a class-E power amplifier to ensure that the output signal power is large enough and a demodulator to demodulate the received data is implemented to cooperate with the stimulator. The proposed stimulator has been fabricated in a 0.35-um CMOS process. The total chip area is 0.865 by 0.904 mm2. The proposed stimulator and the class-E power amplifier consume 27.8 mW and 508 mW with a transmission distance of 5 cm, respectively. The measurement results show that the overall wireless power transfer efficiency is 5.5%.