Self-Calibrating Epiretinal Prosthesis in 65nm CMOS

Since their conception and success in human trials, the flexibility and spatial resolution of retinal prostheses have been of major interest. Clinical studies have revealed that hundreds of channels are needed to restore functional visual perception [1], and more sophisticated waveforms present advantages over biphasic pulses [2]. Initial designs targeted stimulation current levels up to 1mA to ensure functionality. For such designs, an output compliance of >10V was required [2,3], and HV technologies were used at the expense of area and power consumption [2-6]. Human clinical trials have recently shown that implanted electrodes present a stimulus threshold as low as 50μA [1]. In addition, advances in implant technology promise close placement of electrode array and retinal tissue, which can further decrease the required current. Thus, highly scaled LV technologies can provide alternative means to reduce area and power, and to support hundreds of flexible independent channels for fully intraocular implants. In this paper, a self-calibrating 512-channel epiretinal prosthesis in 65nm CMOS is presented. It features dual-band telemetry for power and data, clock recovery, a 2-step calibration technique to match biphasic stimulation currents, and an independent arbitrary output waveform per channel. The implant integrates coils (power and data), IC, external capacitors and electrode array using a biocompatible parylene substrate, providing a fully intraocular solution.