A fully integrated 265V_RMS input AC-DC interface is demonstrated in a 0.35μm CMOS technology, needing only 1 external low voltage SMD capacitor for improved performance. The converter can directly interface the universal line voltage (50-60Hz) and converts this into a regulated DC voltage of 3.3V. High input voltage operation is made possible through custom layout of high voltage capable passive components. A model of an ideal AC-DC capacitive step-down converter is presented and the proposed circuit architecture is designed to approach maximum attainable power throughput. The prototype converter demonstrates a maximum output power of 287μW on a die area of 6mm² and enables integrated circuits to be supplied straight from the ubiquitus mains voltage. Hereby circumventing the need for traditional converters using high voltage discrete components.