A Passive-Stacked Third-Order Buck Converter With Inherent Input Filtering Achieving 0.7-W/mm $^{2}$ Power Density and 94% Peak Efficiency

This letter describes a passive-stacked third-order buck (PS3B) converter that offers loss-, structure-, and noise-related benefits as compared to a conventional buck converter. Specifically, all the passives including two inductors are stacked in a packaging-friendly manner at the PS3B converter input, allowing for the inductors to process lower current than a conventional buck converter while inherently filtering input current noise. A prototype shows that the converter achieves a peak efficiency of 94% and a peak power density of 0.7 W/mm
²
.