A 1,224-Channel 60 μm Pitch Active Closed-Loop Stimulator for Selective Retinal Ganglion Cell Type Activation

To match the electrical stimulation responses of Retinal Ganglion Cells (RGCs) to their natural light responses, the different Ganglion Cell subtypes need to be stimulated selectively. A promising way to achieve this in future retinal implants is the use of sinusoidal stimulation currents in the kilohertz range. This paper presents a closed-loop current controlled stimulation and recording system on chip (SoC) with the ability to independently deliver mixed frequency waveforms with arbitrary amplitudes on each of the 1,224 $60~ \mu \mathrm{m}$ pitch output channels. The design was fabricated using a $180 \mathrm{~nm}$ CMOS process.