Scaleable Output, and Bidirectional Radio-Frequency Telemetry

Abstract—100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application-specific integrated circuit (ASIC) has been designed, constructed and tested. The ASIC forms a significant milestone and an integral compo-nent of a 100-electrode neurostimulation system being developed by the authors. The system comprises an externally worn transmitter and a body implantable stimulator. The purpose of the system is to communicate both data and power across tissue via radio-fre-quency (RF) telemetry such that externally programmable, con-stant current, charge balanced, biphasic stimuli may be delivered to neural tissue at 100 unique sites. An intrinsic reverse telemetry feature of the ASIC has been de-signed such that information pertaining to the device function, re-construction of the stimulation voltage waveform, and the measure-ment of impedance may be obtained through noninvasive means. To compensate for the paucity of data pertaining to the stimula-tion thresholds necessary in evoking a physiological response, the ASIC has been designed with scaleable current output. The ASIC has been designed primarily as a treatment of degen-erative disorders of the retina whereby the 100 channels are to be utilized in the delivery of a pattern of stimuli of varying intensity and or duty cycle to the surviving neural tissue of the retina. How-ever, it is conceivable that other fields of neurostimulation such as cochlear prosthetics and functional electronic stimulation may benefit from the employment of the system. Index Terms—Neurostimulator, retina, telemetry, vision pros-thesis, VLSI. I