915-MHz wireless 64-channel neural recording SoC with programmable mixed-signal FIR filters

Abstract

A system-on-chip (SoC) neural recording interface with 64 channels, 64 16-tap programmable mixed-signal FIR filters and a fully integrated 915MHz OOK/FSK closed-loop wireless transmitter is presented. Each recording channel has a fully differential amplifier with 54dB of gain and utilizes a tunable low-distortion subthreshold MOS-resistor to reject DC offsets with an input-referred noise of 6.5μV and a CMRR of 78dB. Each channel contains a modified 8-bit SAR ADC with an ENOB of 7.8-bits and can provide analog-digital multiplication by modifying the the sampling phase of the ADC. It is used in conjunction with 12-bit digital adders and registers to implement 64 programmable transposed FIR filters that enable precise separation of various bands in the neural spectrum. The 915MHz FSK/OOK transmitter offers data rates up to 1.5Mbps with a maximum output power of 0dBm. The 4×3mm chip fabricated in a 0.13μm CMOS process dissipates 5.03mW from a 1.2V supply.