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Published December 2013 | public
Journal Article

A Fully Intraocular High-Density Self-Calibrating Epiretinal Prosthesis


This paper presents a fully intraocular self-calibrating epiretinal prosthesis with 512 independent channels in 65 nm CMOS. A novel digital calibration technique matches the biphasic currents of each channel independently while the calibration circuitry is shared among every 4 channels. Dual-band telemetry for power and data with on-chip rectifier and clock recovery reduces the number of off-chip components. The rectifier utilizes unidirectional switches to prevent reverse conduction loss in the power transistors and achieves an efficiency > 80%. The data telemetry implements a phase-shift keying (PSK) modulation scheme and supports data rates up to 20 Mb/s. The system occupies an area of 4.5 ×3.1 mm^2. It features a pixel size of 0.0169 mm^2 and arbitrary waveform generation per channel. In vitro measurements performed on a Pt/Ir concentric bipolar electrode in phosphate buffered saline (PBS) are presented. A statistical measurement over 40 channels from 5 different chips shows a current mismatch with μ = 1.12 μA and σ = 0.53 μA. The chip is integrated with flexible MEMS origami coils and parylene substrate to provide a fully intraocular implant.

Additional Information

© 2013 IEEE. Manuscript received October 18, 2013; revised December 10, 2013; accepted December 19, 2013. Date of publication January 20, 2014; date of current version January 28, 2014. This work was supported by NSF Biomimetic Micro-Electronic Systems—Engineering Research Center (BMES-ERC). This paper was recommended by Associate Editor S. Gambini. The authors acknowledge the contributions of M. Loh and J. Yoo for insightful technical discussions, A. Wang for assistance with the experimental work, and TSMC for chip fabrication.

Additional details

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October 26, 2023