臺灣博碩士論文加值系統

本篇論文提出及分析應用於下視網膜互補式金氧半太陽能電池256像素刺激晶片移植系統，晶片採用台積電0.18um互補式金氧半CIS製程工藝，尺寸為3.2mm x 3.2mm。在紅外光強為96 mW/cm2,訊號光源為15,000Lux確保最大刺激，量測晶片產生的電刺激，最大刺激電流為12.4uA，刺激頻率為17.5Hz。
晶片架構採用雙向共用電極(BDSEs)搭配分區供電方式(DPSS)，使電極面積在相同晶片面積下提升，進而將刺激電荷大幅提升至15.3nC。另外，採用具跨導放大器的積分器來提升光電流積分時的線性度。且利用調整背景光消除電路中的電流源，使影像動態範圍提升至30.19dB，最大可感測光強為9393Lux。接著，利用鍍有具生物相容性的IrOx之晶片進行體外實驗，驗證晶片產生的電刺激能有效使rd1老鼠的視網膜神經節細胞產生相對應的反應。
在下一版改善的電路模擬結果中，顯示利用自動適應光源像素電路，能讓主動式像素元件和人眼一樣適應不同數量級的光強，使晶片在一般使用強度下，影像動態範圍提升至60dB，最小和最大感測光強分別為100Lux和100,000Lux。在和上一版相同刺激電荷下，最大功耗也因採用自動適應光源像素電路而下降至原先的1.94倍。改良的刺激器可輸出恆定電流雙向刺激，雙向刺激電流差由原先的34.2%縮小至0.74%，刺激電荷差由原先的53.9%縮小至2.76%。且在分區供電的基礎下，更改同時刺激的像素排列方式，使同時刺激不同像素之間最大刺激電荷差由上一版的30%縮小至12.2%，且最大誤刺激只有0.91nC並不會達到有效刺激。

A photovoltaic-cell-powered CMOS 256-pixel subretinal chips is fabricated by 180-nm CIS technology. The maximum stimulation current is 12.4uA with stimulation frequency of 17.5Hz under the illumination of 15,000lux signal light source and 96mW/cm2 IR intensity. The stimulation charge is increased significantly with the implementation of bidirectional-sharing electrodes (BDSEs) to 15.3nC. Also, the current integrator consists of an OTA is used to improve the linearity of photocurrent integration. The image dynamic range is increased to 30.19dB with the maximum detectable illuminance of 9393Lux with larger unit current source in the proposed adaptive background cancellation circuit (ABCC). In vitro patch clamp experimental results with the retinas of rd1 mice show that the proposed subretinal chip can stimulate and generate ganglion cell responses, which follows the stimulation frequency of 11.3Hz.
In the modified chip design, the adaptation of different image light intensities mimics the logarithmic responsivity of the photoreceptor in the human retina with the modified auto-adaptive pixel circuit. The image dynamic range is raised further to 60dB with minimum detectable illuminance of 100Lux and with maximum detectable illuminance of 10,000Lux. Under uniform light illumination, the photo response curve works in a range of two orders of magnitude as human retina. The maximum power consumption is decreased 1.94 times compared with the previous chip. Also, the current mismatch of biphasic stimulation is decreased significantly from 34.2% to 0.74% and the charge mismatch is decreased from 53.9% to 2.76% with the modified constant current stimulator (CCS). Furthermore, the difference of stimulation charge at the same phase is greatly reduced from 30% to 12.2% compared with the previous chip with the new phase configuration in divisional power supply scheme (DPSS). In addition, the maximum cross-talk is 0.91nC, which is below the stimulation threshold charge.

CONTENTS
ABSTRACT (CHINESE) i
ABSTRACT (ENGLISH) ii
ACKNOWLEDGEMENTS iv
CONTENTS v
TABLE CAPTIONS vii
FIGURE CAPTIONS viii

CHAPTER 1 INTRODUCTION 1
1.1 Background 1
1.2 Review on the Subretinal Prostheses 4
1.3 Motivation 9
1.4 Main Results 11
1.5 Thesis Organization 13
CHAPTER 2 CHIP ARCHITECTURE AND CIRCUIT DESIGN 15
2.1 System And Chip Architecture 15
2.2 Circuit Design 21
2.2.1 Divisional Power Supply Scheme (DPSS) and Bidirectional-Sharing Electrodes (BDSEs) 21
2.2.2 Two-dimensional Equivalent Electrode Model for Cross-talk Simulation 24
2.2.3 Adaptive Background Cancellation Circuit (ABCC) and Pixel Circuit 29

2.2.4 Charge Pump Circuit [27] and Control Signal Generator [29] 35
2.3 Temperature Measurement using On-Chip NPN transistor 41
2.4 Post Simulation Results 45
CHAPTER 3 EXPERIMENTAL RESULTS 48
3.1 Measurement Results of Subretinal Chips 48
3.1.1 Measurement Setup 48
3.1.2 Measurement Results 53
3.2 In Vitro Results of Subretinal Chips 60
3.2.1 Measurement Setup 60
3.2.2 Measurement Results 62
3.3 Discussion 64
CHAPTER 4 Modified Circuit Design 68
4.1 Circuit Design 68
4.1.1 Auto-Adaptive Pixel Circuit [45] 69
4.1.2 Constant Current Stimulator (CCS) 71
4.1.3 Voltage Regulation Circuit 73
4.1.4 Phase Configuration in DPSS 75
4.2 Post Simulation Results 77
4.3 Discussion 80
CHAPTER 5 Conclusions and Future Work 81
5.1 Conclusions 81
5.2 Future Work 82

REFERENCES 83
VITA 90

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