A Bi-Directional Neural Interface Chip With 32-Channel 83-dB DR CTDSM-Based Recording Using FIRDAC With Pre-Emptive ELD Compensation

Clinical-ready neuromodulation devices for real-time monitoring and treatment of neurological disorders require a neural interface integrated circuit (IC) that supports therapeutic neurostimulation together with concurrent recording of neural activities from large brain regions. To address this need, this article presents an IC with 32 high dynamic range (HDR) electrocorticography (ECoG) recording channels and two programmable neurostimulators allowing bi-directional neural interfacing. The recording channel uses a 2nd-order continuous-time $\Delta \Sigma $ modulator (CTDSM) architecture with 12-tap finite impulse response digital-to-analog converter (FIRDAC) feedback facilitated by a pre-emptive current-steering excess loop delay (ELD) compensation scheme. By employing a high-performance linearized low-noise/low-power transconductance amplifier (L³TA) in the input integration stage, the recording channel achieves 83-dB dynamic range (DR) with up to 222-mV_pp linear input range, and thus can accommodate large electrode dc offsets (EDOs) and stimulation artifacts. Thanks to the FIRDAC that relaxes component matching requirements, each recording channel occupies only 0.028 mm² and consumes $5.39~{\mu }$ W while being manufactured in standard 180-nm CMOS technology. The concurrent neural recording and stimulation capabilities of the chip have been validated in a mouse experiment in vivo, which shows that the recording channel can tolerate real stimulation artifacts and the recorded ECoG signals can be separated from the artifacts with high fidelity.