Yihan Zhang and K. L. Shepard, “A 0.6-mm2 powering and data telemetry system compatible with ultrasound b-mode imaging for freely moving biomedical sensor systems,” Custom Integrated Circuits Conference, 2019
A 0.6 mm2 integrated circuit, fabricated in a 180 nm process, is designed to operate within the field of view of an ultrasound B-mode imager, allowing data to be received from ultra-small-form-factor devices that can be localized, powered, and configured as multiple freely moving ingestible or implantable systems. Power is harvested from ultrasound pulses emitted by the imaging transducer array and a bi-directional data link is established that is synchronized to the frame rate of the imager. The chip consumes 57 pW of power and supports data rates of 25 bit/s for uplink and 50 bit/s for downlink for an imager operating at 50 frames per second. Fully packaged within 11 mm3 with a piezoelectric transducer, the chip enables tissue implants as deep as 71 mm. Real-time localizations of devices is possible within the field of view of the imager at 0.8-mm accuracy. An on-chip instruction set allows for software configuration and a smooth transition to a more power-intensive mode of operation using focused ultrasound pulses after localization, with 280 nW power delivery verified using 0.5% duty cycle ultrasound.