An Electrical Stimulator IC with Chopped Pulse based Active Charge Balancing for Neural Interface Applications

In this paper, a current-mode neural stimulator integrated circuit (IC) using novel active charge balancing technique is presented. The charge balancing technique proposed in this work is based on chopped pulse waveform, where the number of chopped pulses generated in the anodic phase is controlled accurately in order to limit the amount of residual potential at the electrode. In addition, a quick automatic electrode shorting process follows the active charge balancing phase to further discharge to a negligible residual voltage level in every stimulation cycle, ensuring a safe and long-term operation. Both symmetric and asymmetric stimulation pulse waveforms can be selected to provide wide flexibility for various stimulation environment. The stimulator IC designed using 0.18-µm standard CMOS process achieves 12.3 V of voltage compliance and can deliver 1 mA of maximum stimulation current with 5-bit resolution and high linearity. All circuit functions are integrated on-chip without external components, and the fabricated chip consumes only 0.095 mm² of active die area.