A 0.01-mm2 Mostly Digital Capacitor-Less AFE for Distributed Autonomous Neural Sensor Nodes

This letter presents a miniaturized neural recording analog front-end (AFE) suitable for distributed sub-mm neural recording implants. Including reference generators, this AFE occupies an area of only 0.01 mm
²
, thanks to a mostly digital architecture with more than half of area being scalable digital logic. Implemented in 65-nm CMOS, the AFE is measured to consume 3.2
$ {\mu }\text{W}$
of power from 0.6-V supply, and achieves an input-referred noise of 2.2
$ {\mu {\mathrm{ V}}}_{\mathrm{rms}}$
over 500 Hz of bandwidth. The AFE is validated by integrating it into a neural sensing SoC with wireless power and data telemetry.
In vitro
experiments demonstrate reliable recording of the AFE in a fully wireless environment.