A2 4 µW, Batteryless, Crystal-free, Multinode Synchronized SoC “Bionode” for Wireless Prosthesis Control Hansraj Bhamra, Student Member , IEEE, Y oung-Joon Kim,Student Member , IEEE, Jithin Joseph, John Lynch, Oren Z. Gall, Henry Mei, Student Member , IEEE, Chuizhou Meng, Jui-Wei Tsai

Abstract

We present a batteryless, crystal-free, time division multiple access (TDMA) synchronized multinode wireless body sensor node (WBSN) system-on-chip (SoC), referred to as a Bionode, for continuous and real-time telemetry of electromyo- grams (EMGs), enabling intuitive upper limb prosthesis control by an amputee. The SoC utilizes state of the art in supercapacitive RF energy harvesting, biosensing analog-front-end, switching- optimized SAR ADC, ultra-low-power RF transceiver, and clock circuits. The sensor node SoCs are time synchronized with a base station, mounted on the prosthetic arm, by using the ultra-low- power TDMA controller and receiver, and the digital core circuits. A 915 MHz broadcast RF signal is utilized to synthesize the car- rier frequency of the transmitter . This along with the process and voltage compensated on-chip clock obviates the need for a bulky crystal oscillator, thus providing a low-cost and highly integrated solution to the WBSNs. The SoC is verified by capturing the EMG data from a healthy human body and consumes only 24 µW, while operating exclusively from the harvested RF energy. Implemented in a 0.18 µm CMOS process, the SoC occupies 2.025 mm 2 silicon area. The sensor node has an extremely low weight and phys- ical dimensions, thanks to the flexible carbon nanotube (CNT) supercapacitor, electrically small antenna (ESA), and crystal-free operation of the SoC.