A single-inductor dual-output switching converter with low ripples and improved cross regulation

This paper proposes a novel fly capacitor method for single-inductor dual-output (SIDO) switching converters to reduce the output ripples and spikes. An adaptive common-mode control is presented to suppress the cross regulation problem. The converter can automatically switch between pulse-width modulation (PWM) and pulse-frequency modulation (PFM) control to improve the efficiency. The SIDO converter is specified for one channel 1.2 V/400 mA and the other 1.8 V/200 mA with input voltage ranging from 2.7 V to 5 V. The chip has been fabricated on a 0.25 mum CMOS mixed signal process. The conversion efficiency is 82% at a total output power of 840 mW while the output ripples are about 20 mV and spikes less than 40 mV.