A 1.5-GHz Fully Integrated DC–DC Converter Based on Electromagnetically Coupled Class-D LC Oscillators and Resonant LC Flying Impedance Achieving 4.1-W/mm2 Peak Power Density and 77% Peak Efficiency

This letter introduces a fully integrated DC–DC converter based on electromagnetically coupled class-D LC oscillators (EMLC) manufactured in a 22nm FDSOI CMOS process. The proposed converter implements a resonant LC flying impedance that improves the EMLC output resistance by accomplishing a resonant charge transfer between the flying capacitor CFLY and the load capacitor CO. This design achieves 77% peak efficiency and 4.1 W/mm2 peak power density in a total area of 0.33 mm2. The output voltage is regulated with a duty cycling scheme from 0.003 W/mm2 up to 2.1 W/mm2 with < 2% efficiency loss.