A 16-Output 10-V Compliant Stimulator ASIC With Sub-10-nA Mismatch and Simultaneous ETI Sensing for Selective Neural Stimulation

This article presents a 16-output high-voltage (HV) compliant stimulator ASIC for selective neural stimulation. The ASIC supports temporal interference stimulation (TIS) to achieve high-spatial selectivity without requiring nerve-penetrating electrodes. A novel on-the-fly active charge balancing (CB) is proposed since existing CB solutions cannot be directly applied to TIS. Simultaneous electrode-tissue impedance (ETI) sensing is realized by reusing the CB hardware. The stimulator ASIC, fabricated in 130-nm bipolar-complementary metal-oxide-semiconductor-double-diffused metal-oxide-semiconductor (BCD) technology, occupies 0.29 mm ^{2} per output and achieves 10-V compliance while supporting up to 10-mA stimulation current and maintaining TIS steering flexibility. The proposed active CB approach compensates for electrode voltage drift during TIS based on a negative feedback loop, achieving a sub-10-nA mismatch current over a wide range of ETIs. The ETI sensing reuses the stimulation current and CB hardware for simultaneous measurements during stimulation, achieving a sensing inaccuracy of \pm 2 \Omega . Extensive saline experiments confirm the ability of the ASIC to achieve superior spatial selectivity for stimulation while maintaining proper active CB and simultaneous ETI sensing.