Energy Harvesting is crucial to the development of miniaturized implants to achieve minimal invasiveness and system autonomy. While RF wireless power transfer suffers from substantial tissue attenuation, a wireless piezoelectric energy harvester (PEH) is more attractive for deep-tissue implant applications [1]. Typical PEH interfaces with a full-bridge rectifier for AC-DC conversion with limited extractable electrical power due to the PEH inherent capacitance (Cp). The parallel-synchronized-switch harvesting-on-inductor (P-SSHI) technique [2, 3] can increase the output energy by flipping the PEH voltage using resonance, whereas other techniques in [4] and [5] focus on boosting the PEH voltage swing to increase the extracted power. Yet, all of them require a bulky external high-Q inductor (up to the mH range in [3] and [5]) to ensure a high power-extraction enhancement. This work reports an inductorless fully integrated PEH interface, achieving a high voltage flipping efficiency (ηF) of 0.85 and a maximum output-power increasing rate (MOPIR) of 4.83× when compared with a full-bridge rectifier interface. © 2017 IEEE.