Track-and-Zoom Neural Analog-to-Digital Converter With Blind Stimulation Artifact Rejection

Abstract

Closed-loop neuromodulation for the treatment of neurological disorders requires monitoring of the brain activity uninterruptedly even during neurostimulation. This article presents a bidirectional 32-channel CMOS neural interface that can record neural activity during stimulation. Each channel consists of a dc-coupled $\Delta ^{2} \Sigma $ -modulated analog-to-digital converter (neural-ADC), which records slow potentials ( $\Delta ^{2} \Sigma $ -ADC consumes 1.7 $\mu \text{W}$ from 0.6-V/1.2-V digital/analog supplies and time-shares the modulator’s feedback DAC as the multi-bit current-mode stimulator operating at 3.3 V. The ADC occupies a silicon area of 0.023 mm2 in the 130-nm CMOS and achieves a signal-to-noise-and-distortion ratio (SNDR) of 70 dB over the 500-Hz bandwidth and an equivalent noise efficiency factor (NEF) of 2.86 without a stand-alone front-end amplifier. The 32-channel bidirectionally interfacing prototype is validated in the in vivo whole brain of a rodent.