Artificial Retina Signal Processing Circuit

Signal processing circuit of the artificial retina is used to restore vision for patients with visual impairment due to outer retinal degenerative diseases (such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD)), The core of the circuit consist of wireless power supply, data demodulation and stimulation driver circuit, the chip receives commands from external transmitter signal, and drive a current pulse electrode array to stimulate the retinal nerve cells, so that the blind or near-blind patients can return part of the vision.The technology still faces enormous challenges, such as the stability of internal power supply, wireless signal transmission efficiency, signal encoding method of the optic nerve stimulation, the chip's long-term stability and bio-compatibility.In the beginning, the basic structure and working principle of artificial retina signal processing circuit is analyzed, then conducted a system-level chip research and design, set the electrical characteristics, analyzes the design considerations in various modules in the system, researches improvement program of each module, then complete the design,simulation and layout, the test results is given at last.An artificial retina signal processing circuit is designed based on the CSMC0.5μm standard CMOS process with Cadence simulation platform in this paper, the circuit consists of CMOS rectifier circuit, capacitor-less low dropout linear regulator (LDO) and wireless signal receiving circuit, the design is a full-chip integrated circuit, through external transmit13.56MHz ASK signal to obtain a stable energy and data, simulation results show that, CMOS rectifier circuit can convert the input ASK signal voltage into3.8V;capacitor-less LDO linear regulator can produce a stable3.3V power supply, the maximum output current capability up to40mA, and have good stability and transient response; ASK demodulation circuit can correctly demodulate the input signal in a large frequency range (1MHz～30MHz),and the minimum demodulation index of the ASK signal is11%. Finally, the chip is tested and shows that the CMOS rectifier circuit and capacitor-less LDO's features and performance can meet the design requirements and the needs of implantable systems.