90% High Efficiency and 100-W/cm$^{\bm 3}$ High Power Density Integrated DC–DC Converter for Cellular Phones

This paper describes a small-size buck-type dc–dc converter for cellular phones. Output power MOSFETs and control circuitry are monolithically integrated. The newly developed pulse frequency modulation control integrated circuit, mounted on a planar inductor within the converter package, has a low quiescent current below 10 μA and a small chip size of 1.4 mm × 1.1 mm in a 0.35-μm CMOS process. The converter achieves a maximum efficiency of 90% and a power density above 100 W/cm $^3$ .