The design of CMOS self-powered 256-pixel implantable chip with on-chip photovoltaic cells and active pixel sensors for subretinal prostheses

A photovoltaic-cell-powered CMOS 256-pixel implantable chip is proposed for subretinal prostheses. In the proposed chip, the divisional power supply scheme (DPSS) and the active pixel sensor (APS) are adopted to improve the efficiency of output stimulation currents and the image sensitivity. The proposed chip consists of a 16×16 photodiode array with 8 DPSS divisions, control signal generator circuits, and photovoltaic cells. It is designed and fabricated in 180-nm CMOS image sensor (CIS) technology. The chip size is 3mm × 3mm. The measured frequency of eight-phase control signals is 47.68 Hz under signal light intensity of 5 mW/cm² and background IR intensity of 80 mW/cm². The measured output stimulation current is 19.9 0 μA under 10-kΩ load. Under the equivalent electrode impedance load, the measured frequency of eight-phase control signals is 45.45 Hz. The measured peak output stimulation current is 19.52 μA and the amount of injected charges per pixel is 4.03nC. The measurement results have verified the correct function of the proposed subretinal implant chip.