Rail-to-Rail-Input Dual-Radio 64-Channel Closed-Loop Neurostimulator

Abstract

A 64-channel 0.13-μm CMOS system on a chip (SoC) for neuroelectrical monitoring and responsive neurostimulation is presented. The ΔΣ-based neural channel records signals with rail-to-rail dc offset at the input without any area-intensive dc-removing passive components, which leads to a compact 0.013-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> integration area of recording and stimulation circuits. The channel consumes 630 nW, yields a signal to noise and distortion ratio of 72.2 dB, a 1.13-μVrms integrated input-referred noise over 0.1-500 Hz frequency range, and a noise efficiency factor of 2.86. Analog multipliers are implemented in each channel with minimum additional area cost by reusing the multi-bit current-digital to analog converter that is originally placed for current-mode stimulation. The multipliers are used for compact implementation of bandpass finite impulse response filters, as well as voltage gain scaling. A tri-core low-power DSP conducts phase-synchrony-based neurophysiological event detection and triggers a subset of 64 programmable arbitrary-waveform current-mode stimulators for subsequent neuromodulation. Two ultra-wideband (UWB) wireless transmitters communicate to receivers located at 10 cm to 2 m distance from the implanted SoC with data rates of 10-46 Mb/s, respectively. An inductive link that operates at 1.5 MHz provides power to the SoC and is also used to communicate commands to an on-chip ASK receiver. The chip occupies 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while consuming 1.07 and 5.44 mW with delay-based and voltage controlled oscillator-based UWB transmitters, respectively. The SoC is validated in vivo using epilepsy monitoring (seizure detection) and treatment (seizure suppression) experiments.