An ac-coupled wideband neural recording front-end with sub-1 mm2×fj/conv-step efficiency and 0.97 nef

Official URL: https://dx.doi.org/10.1109/LSSC.2020.3013993

This letter presents an energy-And-Area-efficient ac-coupled front-end for the multichannel recording of wideband neural signals. The proposed unit conditions local field and action potentials using an inverter-based capacitively coupled low-noise amplifier, followed by a per-channel 10-b asynchronous SAR ADC. The adaptation of unit-length capacitors minimizes the ADC area and relaxes the amplifier gain so that small coupling capacitors can be integrated. The prototype in 65-nm CMOS achieves 4\times smaller area and 3\times higher energy-Area efficiency compared to the state of the art with 164 \mu \text{m}\times 40\,\,\mu \text{m} footprint and 0.78 mm ^{2}\times fJ/conv-step energy-Area figure of merit. The measured 0.65-\mu \text{W} power consumption and 3.1-\mu \text{V}_{\mathrm{ rms}} input-referred noise within 1 Hz-10 kHz bandwidth correspond to a noise efficiency factor of 0.97.