An Inductively-Powered Wireless Neural Recording System With a Charge Sampling Analog Front-End

An inductively-powered wireless integrated neural recording system (WINeR-7) is presented for wireless and battery-less neural recording from freely-behaving animal subjects inside a wirelessly powered standard homecage. The WINeR-7 system employs a novel wide-swing dual slope charge sampling (DSCS) analog front-end (AFE) architecture, which performs amplification, filtering, sampling, and analog-to-time conversion with minimal interference and small amount of power. The output of the DSCS-AFE produces a pseudodigital pulse-width modulated (PWM) signal. A circular shift register time-division multiplexes (TDM) the PWM pulses to create a TDM-PWM signal, which is fed into an on-chip 915-MHz transmitter (Tx). The AFE and Tx are supplied at 1.8 and 4.2 V, respectively, by a power management block, which includes a high efficiency active rectifier and automatic resonance tuning, operating at 13.56 MHz. The eight-channel system-on-a-chip was fabricated in a 0.35- $mu text{m}$ CMOS process, occupying $5 times 2.5$ mm2 and consumed 51.4 mW. For each channel, the sampling rate is 21.48 kHz and the power consumption is 19.3 $mu text{W}$ . In vivo experiments were conducted on freely-behaving rats in an energized homecage by continuously delivering 51.4 mW to the WINeR-7 system in a closed-loop fashion and recording local field potentials.