A 0.00175 mm2/channel Direct-Digitization Frontend with Automatic EDO/Drift Compensation for Floating Subcortical Neural Probes

This paper presents a recording front end for modular CMOS neural probes featuring on-site direct digitization with high-spatial resolution. The architecture is based on a folded-cascode OTA-C two-step delta-sigma converter featuring 4-channel time-multiplexing. The integrated automatic commonmode adjustment covers a range of 97.7 mV for electrode DC offset and drift compensation. An integrated noise of $7.59 \mu \mathrm{~V}_{\mathrm{rms}}$ is achieved in the full bandwidth from $D C$ to 10 kHz. The total power consumption amounts to $9.2 \mu \mathrm{~W} /$ channel including digital interfacing with a supply voltage of 1.2 V. The front end is implemented in a 180 nm SOI process on an area of $0.00175 \mathrm{~mm}^{2} / \mathrm{ch}$. enabling full integration below the recording electrodes of a 192-channel probe with 5 external pads and a two-column electrode pitch of $35 \mu \mathrm{~m}$.