This article presents a novel control system for a regulated resonant switched-capacitor point-of-load converter, together with its steady-state and small-signal analyses. The output voltage is regulated through a combined frequency/phase shift on-chip controller that operates, thanks to a zero-crossing detector for the tank current. By using such a control technique, voltage regulation can be achieved for a wide range of conversion ratios. Different operation modes are adopted to maximize the efficiency at every load condition. A prototype based on an ASIC developed in a 130-nm CMOS technology has been designed, which achieves the 2.5 to 0.8-1.35 V conversion and supplies up to 3 A. The external resonant tank is composed of a 12 nH air-core inductor and a 4.7 mu F capacitor in a 0805 package, achieving high power density. The converter efficiency is demonstrated to be similar to that of an integrated buck converter designed for the same application, whereas the inductor size is reduced by a factor of eight.
