An Optically Addressed Nanowire-Based Retinal Prosthesis With Wireless Stimulation Waveform Control and Charge Telemetering

Current retinal prostheses (RPs) have not achieved useful vision restoration, as their resolution is limited by power dissipation and complexity of interconnect. This article presents an inductively powered wireless system on a chip (SoC) for an electrically controlled, optically addressed retinal prosthetic system. The SoC interfaces to a co-fabricated nanoengineered photosensitive electrode array using only two wires. To reduce the thermal dissipation near sensitive retinal tissue, the proposed design pushes voltage regulation and charge-balanced stimulation control off the implant via a duty-cycled wireless charge metering technique. A calibration technique compensating for power fluctuation caused by eye movement is also presented. Implemented in 180-nm CMOS and delivering up to
$3~\mu \text{C}$
of charge at 20-nC resolution, the SoC achieves 73% RF-to-stimulation power efficiency.