A Single-Inductor Multiple-Output Auto-Buck-Boost DC–DC Converter With Autophase Allocation

Abstract

A single-inductor multiple-output (SIMO) converter with auto-buck-boost feature is presented in this paper. A seamless auto-buck-boost scheme for SIMO dc–dc converter using time-multiplexing control is proposed. Additionally, with the proposed first-order phase-locked loop (FOPLL) and autophase allocation, this circuit solves the problem of unbalanced loadings of different channels, and it also keeps the locking time of the inductor current sufficiently short to minimize average inductor current for attaining higher efficiency. By combining with all channel controllers, FOPLL not only allows fast load-transient response without degrading the power efficiency, but it also reduces controller order of the frequency control loop, attenuates the noise injected from charge pump, and achieves robust stability. The scheme enables the dc–dc converter to operate from wide input and output ranges. Implemented in a 0.35-μm CMOS technology, the chip area is 5000 μm × 1850 μm, including ESD test pads. The switching frequency is fixed at 0.25 MHz. The load-transient response time is less than 100 μs. The proposed converter achieves a peak efficiency of 89% and maximum output power up to 1.46 W with efficiency of 70%.