An Implantable Power Extraction Circuit with Integrated PMUTs for Wireless Power Delivery

Abstract

A power-extraction IC (PEC) capable of extracting and boosting ultrasound energy to power ultra-lowpower medical implants is presented. This work focusses on circuits that can convert extremely low levels of incident energy as would typically be found in deep-tissue miniaturized implants. The PEC chip is designed to extract energy from a piezoelectric micromachined ultrasonic transducer (PMUT) array operating at 2.5MHz. It can self-start with a similar to 48mVp AC input voltages. The PEC was designed and implemented in Silterra 0.13 mu m PMUTs-on-CMOS process, which makes ultrasonic wireless power delivery (UWPD) using monolithically integrated PMUTs possible. The PEC harvests ultrasound energy and charges an on-chip 4.5nF capacitor to similar to 1V. From the on-chip capacitor, it can then deliver an average power of 7.9 mu W for 88 mu s to a load. Using an off-chip 0.1 mu F storage capacitor, this can extend to 1.7ms. The chip also included an experimental 5.4mmx5.4mm PMUT array. The fully integrated chip was tested in-vitro and could power a load at 10kPa (3.6mW/cm(2)) received ultrasound pressure.