A 10.2 V 8-Channel Neural Stimulator With Nearly Constant Efficiency Across 90% Current Range and a TDM ADC-Based One-Shot Charge Balancing With < 6 mV Residue

This paper presents an 8-channel current-mode stimulator achieving a ± 10.2V voltage compliance in a standard CMOS process, supporting up to 4.5mA stimulation current per channel. The proposed Dynamic Charge Pump, which adaptively sizes its switches based on the stimulation current, helps achieve 15% higher power efficiency at low currents compared to conventional approaches. We further propose an ADC-based Time-Division Multiplexed (TDM) one-shot charge balancing scheme, where the duration of the second phase is adaptively adjusted to achieve near-zero residual charge on the Electrode-Tissue Interface (ETI). The proposed charge balancing scheme has been validated over a wide range of ETI impedances and achieves a residual voltage below 6mV with an area overhead of only 0.024mm2/channel.