A 45μW Ultrasonic Implantable Wireless Neural Recording Chip Featuring Simultaneous Power Transmission and Backscatter Communication

This paper presents an energy-efficient ultrasonic (US) implantable wireless neural-recording chip comprising a frequency-translating reconfigurable US backscatter modulator, a US power management unit, a clock generation unit, and a data acquisition unit. This is the first integrated circuit designed to enable high-throughput continuous US passive backscatter uplink communication at ultra-low power with uninterrupted US powering. The chip is fabricated in 65 nm CMOS with a total active area of $0.35 \mathrm{~mm}^{2}$. The proposed reconfigurable backscatter modulation achieved a maximum data rate of 220 kbps at ultralow power, resulting in efficiencies of $12.3 \mathrm{pJ} / \mathrm{bit}$ and $23.2 \mathrm{pJ} / \mathrm{bit}$ for OOK and BPSK, respectively, with US transducers spaced by 6 cm in water. This is the most efficient US communication, to our knowledge. The chip was validated in-vitro, with all blocks operating, the chip consumes only $45 \mu \mathrm{~W}$.