Enabling closed-loop neural interface: A bi-directional interface circuit with stimulation artifact cancellation and cross-channel CM noise suppression

We present the first bi-directional neural interface chip that employs a stimulation artifact cancellation circuit to allow concurrent recording and stimulation. In order to further suppress cross-channel common-mode noise, we incorporated a novel common average referencing (CAR) circuit in conjunction with range-adapting (RA) SAR ADC for low-power implementation. The fabricated prototype attenuates stimulation artifacts by up to 42 dB and suppresses common noise among channels by up to 39.8 dB at 330 nW and in an area of 0.17 mm² per channel.