A mm-Sized Implantable Medical Device (IMD) With Ultrasonic Power Transfer and a Hybrid Bi-Directional Data Link Jayant Charthad, Student Member , IEEE , Marcus J. Weber , Student Member , IEEE , Ting Chia Chang , Student Member , IEEE, and Amin Arbabian ,M e mber , IEEE

Abstract

A first proof-of-concept mm-sized implantable device using ultrasonic power transfer and a hybrid bi-directional data communication link is presented. Ultrasonic power transfer en- ables miniaturization of the impla nt and operation deep inside the body, while still achieving safe and high power levels (100 Wt o a few mWs) required for most implant applications. The current implant prototype measures 4 mm 7.8 mm and is comprised of a piezoelectric receiver, an IC designed in 65 nm CMOS process and an off-chip antenna. The IC can support a maximum DC load of 100 W for an incident acoustic intensity that is 5% of the FDA diagnostic limit. This demonstrates the feasibility of providing further higher available DC power , potentially opening up new implant applications. The proposed hybrid bi-directional data link consists of ultrasonic downlink and RF uplink. Falling edge of the ultrasound input is detected as downlink data. The implant transmits an ultra-wideband (UWB) pulse sequence as uplink data, demonstrating capability of implementing an energy-effi- cient M-ary PPM transmitter in the future.