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A high-precision implantable pressure sensor with ultrasonic power-up and data uplink is presented. The fully packaged implant measures $1.7 \times 2.3 \times 7.8$ mm3 and includes a custom IC designed in a 180-nm HV BCD process, a pressure transducer, an energy storage capacitor, and a single piezoelectric transducer (piezo). In order to reduce overall dimensions, unique circuit and system design techniques are presented to enable a single time-multiplexed piezo for both power recovery and data uplink transmission. Implant performance is characterized at significant depths, 12 cm in a tissue phantom, offering a $>13\times $ improvement over state of the art in the depth/volume figure of merit, while demonstrating a robust ultrasonic data uplink with better than 10−5 bit error rate. A transient charging analysis is presented to derive the optimal piezo impedance and charging specifications to maximize overall harvesting efficiency. The IC features a front end with a 10-bit SAR ADC achieving a pressure full-scale range of 800 mmHg with a pressure resolution of 0.78 mmHg, exceeding the requirements for a wide range of in vivo pressure sensing applications. The pressure sampling rate is fully externally controlled, up to 1 ksps, in order to significantly decrease implant energy consumption and to allow for adaptable programming for specific applications. [ABSTRACT FROM AUTHOR]

Miniaturized ultrasonic receivers are designed for efficient powering of implantable medical devices with reconfigurable power loads. Design parameters that affect the efficiency of these receivers under highly variable load conditions, including piezoelectric material, geometry, and operation frequency, are investigated. Measurements were performed to characterize electrical impedance and acoustic-to-electrical efficiency of ultrasonic receivers for off-resonance operation. Finally, we propose, analyze, and demonstrate adaptive matching and frequency tuning techniques using two different reconfigurable matching networks for typical implant loads from 10 \mu \textW to 1 mW. Both simulations and measurements show a significant increase in total implant efficiency (up to 50 percentage points) over this load power range when operating off-resonance with the proposed matching networks. [ABSTRACT FROM AUTHOR]

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 enables miniaturization of the implant and operation deep inside the body, while still achieving safe and high power levels (100 \muW to a few mWs) required for most implant applications. The current implant prototype measures 4 mm\times 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\muW for an incident acoustic intensity that is \sim 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-efficient M-ary PPM transmitter in the future. [ABSTRACT FROM PUBLISHER]