A High-Precision Electrical Stimulator ASIC with Adaptive Charge Balancing for Long-Term Implantable Neuromodulation

High-performance neuromodulators make essential contributions to the treatment of major neurological disorders and quality of life improvement. To enhance therapeutic efficacy and address safety challenges associated with long-term implanted neuromodulators, several high-performance techniques are proposed in this work. Firstly, a novel redundant current mapping (RCM) technology is developed to improve stimulation resolution at minimal area cost. Secondly, a new power-efficient self-adaptive pulse-width calibration (SAPCA) charge-balancing (CB) scheme ensures long-term stimulation safety. Thirdly, several compliance-extension techniques have been developed to achieve a voltage compliance of±11 V. The ASIC is fabricated in a 180-nm Bipolar-CMOS-DMOS (BCD) process with an area of 0.285 mm²/ch. Measurement results show that it achieves 14.5-bit resolution over a 6.5-mA current range and 12.8-bit resolution over a 10-mA current range. The residual voltage (V_res) is reduced from several V to ±5 mV consuming 1.74 μW. Besides, an in vivo experiment demonstrates that the ASIC can maintain CB under long-term stimulation, thereby preserving chronic neuromodulation safety.