The Closed-Loop Neural Interface Available Simultaneously Recording and Stimulation Using Fast Convergence Stimulation Artifact Removal
Abstract
The closed-loop neural interface is actively researched field having broad range of applications. However, it has serious issue that stimulation itself make huge artifacts (~mV) in recording system saturating amplifier, contaminating bio-signal (~ 50V) and the post-analysis during disturbed period. Several stimulation artifact removal (SAR) techniques were presented, but having trade-off between conversion time and algorithm accuracy. Here, we suggested closed-loop neural interface using fast convergence SAR algorithm while sustaining adequate removal accuracy. The amplifier-free ADC-direct 2nd-order continuous delta-sigma modulator recording stage is adopted to provide ~15Vrms input-referred integrated noise from 5Hz to 5kHz which is adequate to record bio-signal. Also, it succeeds to record ~10mV signal about the size of stimulation artifact. The fast-convergence SAR module provides stable accuracy under versatile recording environment. The chip is designed using TSMC 65-nm CMOS process. The Chip is composed of 18 input channels, 2 SAR block, 1 stimulation channel and 2 CIC Filter for down-sampling. The Entire chip area is 1mm2.
