An All-1.8-V-Switch Hybrid Buck–Boost Converter for Li-Battery-Operated PMICs Achieving 95.63% Peak Efficiency Using a 288-m DCR Inductor

In this article, a hybrid step-up/down converter is presented with improved efficiency, smaller form factor, and enhanced reliability for Li-ion-battery-operated power management integrated circuits. Utilizing a hybrid structure with one inductor and two flying capacitors, the dual-path buck–boost (DPBB) converter reduces the average inductor current, switch currents, and the required blocking voltage for the power switches. To support a mid-3-V output from a Li-ion battery, the converter can be realized using 1.8-V rated devices, solely. In addition, the DPBB facilitates a continuous input and output current delivery, thus improving the reliability of the converter significantly. Besides, leveraging the Li-ion battery charge profile, the topology provides an optimal performance during downconversion, in which the converter operates for most of its usage time. With reduced inductor current and smaller voltage rated switches, a more compact inductor with a large dc resistance (DCR) can be used to maintain similar efficiency, which, in turn, helps reduce the converter board space and associated manufacturing cost. Fabricated in a 180-nm BCD technology, the prototype achieves a peak efficiency of 95.63% even for a large 288-m
$\Omega$
inductor DCR with an output ripple below 20 mV for a load current up to 700 mA.