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 . 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 can increase the output energy by flipping the PEH voltage using resonance, whereas other techniques focus on boosting the PEH voltage swing to increase the extracted power. Yet, all of them require a bulky external high-Q inductor to ensure a high power-extraction enhancement. This work reports an inductorless fully integrated PEH interface, achieving a high voltage flipping efficiency (η _F ) of 0.85 and a maximum output-power increasing rate (MOPIR) of 4.83× when compared with a full-bridge rectifier interface.