This paper presents a chip-scale ultralow quiescent current power management system that interfaces with electromechanical energy harvester for enabling self-powering, batteryless wireless sensors. A piezoelectric transducer scavenges and transforms mechanical vibration energy into electricity in ac form, which is then converted into dc power by a full bridge rectifier and collected into a small filter capacitor. A buck–boost converter, as an impedance matching converter to achieve maximum power point tracking, further transfers the energy into a supercapacitor, from which a low-dropout (LDO) regulator powers an on-chip CMOS sensor with clean power supply. Additionally, the energy stored in the supercapacitor can be used to drive a radio frequency transmitter. These components form a complete wireless sensor node, applicable for the Internet of Things sensor networks. The chip is fabricated by using a standard 0.5μm CMOS process. From measurements we have verified all the key merits of this design: first, a high voltage converting efficiency (up to 97.1%) of the rectifier; second, a minimum of 102 s charging time to charge a 1 mF supercapacitor from 0 to 3.3 V of the buck–boost converter with impedance matching method; and third, a 10 nA to 100μA load current range and at least 85° phase margin LDO regulator with ultralow quiescent bias current as low as 750 pA.