This paper presents a vibration-based energy harvesting system composed of a compact electromagnetic (EM) power generator and highly efficient full-wave interface electronics in a system-on-package. The system harvests energy from ambient vibrations, and delivers a smooth and reliable dual rail DC supply to power up a practical load. The energy harvester module is an in-house double-coil EM transducer which generates AC voltage in response to low frequency ambient vibrations. Voltage regulation is achieved by the interface electronics at the core of the system, which is designed to rectify the input AC voltage with peak amplitude ranging from several hundred mVs to several Volts, with maximum efficiency. The interface electronics contains an active rectifier with high conversion efficiency (>80%) for a wide range of load currents (0-42 mu A). A passive network, built from low threshold-voltage chip diodes and capacitors, generates a dual supply voltage from one of the coils to power up the active rectifier. The autonomous system of 16 cm(3) volume (comparable to the size of a C-Type battery), delivers 54 mu W to a 37-mu A load through a dual rail 1.46 V DC voltage with total system efficiency of 81%, when subjected to low frequency (8 Hz) external vibrations. The maximum overall system power density has been validated to be 6.06 mu W/cm(3), three times what was previously reported for a batteryless vibration driven system.