A High-Voltage, Implantable ASIC for Active Interfaces of the Vagus Nerve

Versatility of neural interfaces is a key factor in the efficacy of bioelectronic solutions for treating neurological and cardiac disorders. High-density and highly selective interfaces demand a small form factor, resulting in very high electrode impedances that require a large compliance voltage. This paper presents the design of a low-noise, electrode-driving ASIC in 180-nm high-voltage CMOS technology to achieve concurrent stimulation and recording for vagus nerve interfaces. Inter-channel crosstalk is minimized using pole-shifting. The ASIC has a variable recording gain of 60 to 74 dB and programmable, stimulating currents of 4 to 124 μA, which account for variations in the electrode characteristics. The ASIC occupies an area of 2.31 mm
²
. Measured results show clear biphasic stimulus pulses ranging in widths from 10 to 500 μs. To address the impact of artifacts on biopotential recording, the recording amplifier has a very low input-referred noise of 2.92 μVrms over a variable bandwidth that ranges from 300 Hz to 1.4 kHz or 6.6 kHz with or without pole shifting, respectively.