An All-1.8V-Switch Hybrid Buck-Boost Converter for Li Battery Operated PMICs Achieving 95.63 \% Peak Efficiency using a 288m \Omega DCR inductor

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 (PMICs). 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-3V output from a Li-ion battery, the converter can be realized using 1.8V rated devices, solely. Additionally, 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 down-conversion, 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 reducing 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 20mV for a load current up to 700mA.