11.2 V Supply, 0.21% Biphasic Stimuli Charge-Balanced Neurostimulator With Switching Spike Suppression: An Application to Intraspinal Microstimulation for Restoring Motor Function

In this paper, a new high-voltage and high-current compliance integrated electrical neurostimulator with charge balancing stimuli is presented. The proposed stimulator uses a stacked structure to provide the 11.2 V power supply delivering a biphasic stimulation current of 3.2 mA. It includes a novel charge balancing method to secure safe symmetric and asymmetric biphasic pulse trains with a low charge mismatch of 0.21%. Also, the proposed device properly cancels the switching current spikes generating biphasic stimuli. In addition, two methods based on a gate driver circuit and zero current switching are proposed securing advanced stimulator feature which are validated through extensive testing phase, including a simulation of 29 million periodic stimulation cycles delivering a current of 3.2 mA. The stimulator demonstrates robust performance with an average residual DC current of 11.4 nA after the charge balancing phase. The stimulator is implemented using the standard TSMC 180 nm 1.8 V/3.3 V LV CMOS technology. It operates at a low power budget of $90~\mu $ W. The main core of the circuit occupies an area of 0.181mm2. The fabricated chip has been packaged and successfully tested in a motor function of intraspinal paralysis application.