A 2.3GHz Fully Integrated DC-DC Converter based on Electromagnetically Coupled Class-D LC Oscillators achieving 78.1% Efficiency in 22nm FDSOI CMOS

A fully integrated DC-DC converter based on electromagnetically coupled class-D LC oscillators achieving 0.42-3.2W/mm² power density and 69.4-78.1% efficiency is demonstrated in a 22nm FDSOI CMOS technology. This work proposes on-chip 8-shaped and vertically stacked transformers, which are orthogonally placed for the high-power density, low undesired coupling coefficient and small electromagnetic interference (EMI) radiation. In addition, the output ripple is <10mV without attaching any output capacitor thanks to the 4-phase electromagnetic power delivery scheme. The converter also offers a duty cycled operation mode that enables <2% efficiency degradation down to 100μW. The total chip area is 0.59mm² for 5.9nH inductance (high efficiency version) and 0.22mm² for 3.9nH (high power density versions).