On-Chip Active Pulse-Clamp Stimulation (APCS) for Rapid Recovery, Charge-Balanced Neural Stimulation

Rapid and charge-balanced electrical stimulation is imperative for neurostimulation implants aimed at chronic safety and closed-loop usage. We present an innovative stimulation technique, Active Pulse-Clamp Stimulation (APCS), designed to ensure dependable charge balance with rapid recovery. The APCS technique has two distinctive modes, linear and slewing modes, both incorporated into the on-chip APCS system. APCS employs discrete-time feedback to sense the residual voltage across the electrode's double-layer capacitance, expediting the settling of the electrode interface by either grounding (slewing) or clamping with an amplifier (linear). APCS combines the strengths of both biphasic stimulation and passive recharge, with a customizable recovery time constant set by the user while offering a guaranteed charge balance for safety. To showcase the proof-of-concept for APCS, we implemented the on-chip APCS using a 180nm CMOS process. We demonstrated combined APCS functionality using a benchtop electrode model and a real clinical deep brain stimulation (DBS) electrode in vitro.