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 m CMOS process, occupying 5x2.5 mm(2) and consumed 51.4 mW. For each channel, the sampling rate is 21.48 kHz and the power consumption is 19.3 mu 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.