An Ultra-Low-Power Dual-Channel Analog Front End for Vagus Nerve Sensing with Chopping-Minimized Gain Mismatch

Closed-loop vagus nerve stimulation is a potential efficient treatment for patients suffering from refractory epilepsy. For this therapy, it is necessary to design an ultra-low-power implantable system capable of detecting seizures from the vagus nerve electroneurogram (VENG). The signal acquisition is particularly challenging due to the low amplitude of the signal and the presence of interference from nearby muscles. This work presents an $11.8-\mu \mathrm{W}$ dual-channel analog front end (AFE) specifically tailored for the acquisition of VENG signals, that minimizes interference using calibration and inter-channel chopping. The measurements of the $65-\mathrm{nm}$ CMOS prototype chip show a 55.3- dB rejection of in-band interference, an RMS input-referred noise of $2.03 \mu \mathrm{~V}$ and a bandwidth from 0.3 to 10 kHz, making it suitable for VENG signals acquisition.