Fully Integrated Light-Sensing Stimulator Design for Subretinal Implants
- Authors
- Kang, Hosung; Abbasi, Wajahat H.; Kim, Seong-Woo; Kim, Jungsuk
- Issue Date
- 1-Feb-2019
- Publisher
- MDPI
- Keywords
- subretinal prosthesis; photodiode; high-density pixels; ex-vivo demonstration; light sensor; digital controller; implantable device
- Citation
- SENSORS, v.19, no.3
- Journal Title
- SENSORS
- Volume
- 19
- Number
- 3
- URI
- https://scholarworks.bwise.kr/gachon/handle/2020.sw.gachon/1859
- DOI
- 10.3390/s19030536
- ISSN
- 1424-8220
- Abstract
- This paper presents a fully integrated photodiode-based low-power and low-mismatch stimulator for a subretinal prosthesis. It is known that a subretinal prosthesis achieves 1600-pixel stimulators on a limited single-chip area that is implanted beneath the bipolar cell layer. However, the high-density pixels cause high power dissipation during stimulation and high fabrication costs because of special process technologies such as the complementary metal-oxide semiconductor CMOS image sensor process. In addition, the many residual charges arising from the high-density pixel stimulation have deleterious effects, such as tissue damage and electrode corrosion, on the retina tissue. In this work, we adopted a switched-capacitor current mirror technique for the single-pixel stimulator (SPStim) that enables low power consumption and low mismatch in the subretinal device. The customized P+/N-well photodiode used to sense the incident light in the SPStim also reduces the fabrication cost. The 64-pixel stimulators are fabricated in a standard 0.35-mu m CMOS process along with a global digital controller, which occupies a chip area of 4.3 x 3.2 mm(2) and are ex-vivo demonstrated using a dissected pig eyeball. According to measured results, the SPStim accomplishes a maximum biphasic pulse amplitude of 143 mu A, which dissipates an average power of 167 mu W in a stimulation period of 5 ms, and an average mismatch of 1.12 % between the cathodic and anodic pulses.
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