A multi-channel neural stimulator with resonance compensated inductive receiver and closed-loop smart power management

This paper presents an integrated neural stimulator with highly efficient power management solution, which is intended for a 1024 channel epi-retinal implant. The stimulator features an adaptive high quality LC matching network that compensates for the process variation in the resonance frequency of the inductive receiver and maximizes the link power transmission efficiency. Transcutaneous closed-loop power control is realized that enables optimum power transfer in spite of the coupling variation as well as the variation in the stimulation threshold/current. Finally, a programmable adaptive supply in the high voltage (HV) domain is implemented so to minimize the power dissipation during the active stimulation mode in terms of stimulus current/electrode impedance inconsistencies. The stimulator prototype is designed in AMS 0.35μm HV CMOS technology. In simulation, the power transmission efficiency of the telemetric link is improved by a factor of 2 by the resonance compensation circuits. In addition, automatic supply voltage adaptation of the stimulator from 13.1V to 8V has been achieved, resulting in maximum power saving of 40% for the implantable circuit.