A ±9 V fully integrated CMOS electrode driver for high-impedance microstimulation

A high-voltage electrode driver dedicated to intracortical microstimulation is presented. It is intended to significantly increase the voltage swing in order to maintain constant current stimulation through high-impedance electrode-tissue contacts. Charge pumps are used to generate high-voltage supplies of 8.615 V and -8.348 V from 3.3 V with low ripples (less than 1.6 %) while driving a maximal stimulation current of 200 muA. The negative charge pump architecture has been carefully implemented to suppress latch-up triggering. This high-voltage system is fully integrated and has been implemented with the C08E CMOS 0.8 mum 5 V/20 V process from DALSA Semiconductor. The final output voltage compliance is 14.82 V, allowing constant current stimulation for an implantable in-vivo prototype.