This paper presents a self-powered interface enabling battery-like operation with a regulated 3 V output from ac signals as low as 0.4 V-peak, generated by electromagnetic energy harvesters under low frequency vibrations. As the first stage of the 180 nm standard CMOS circuit, harvested signal is rectified through an ac/dc doubler with active diodes powered internally by a passive ac/dc quadrupler. The voltage is boosted in the second stage through a low voltage charge pump stimulated by an on-chip ring oscillator. The output is finally regulated to 3 V at the last stage. The voltage doubling rectification stage deviates by less than 40 mV from ideal expectation for the validated 0.15-1 V input voltage range. The full system delivers 3 V output to 4.4 M Omega load for input voltage of 0.4 V-peak, which is the lowest operable input voltage in the literature. The demonstrated system generates 9 mu W of dc power with 3 V stable output for 32 mu W input, whereas the circuit is able to supply even more output power for higher input power levels. The maximum efficiency of the rectification stage is 86%, while the full system efficiency is 37% and 28% for unregulated and regulated operation, respectively, when interfaced to an in-house electromagnetic energy harvester under 8 Hz 0.1 g vibration.