Fully integrated DC-DC converter
A 4.1W/mm2 Power Density Fully Integrated DC-DC converter
Over the past years, the constant reduction in the size of consumer electronics has strengthened the demand for fully integrated power management circuits. This work proposes a new fully integrated DC-DC converter topology based on electromagnetically coupled class-D LC oscillators with on-chip transformers and flying capacitors. It relies on adiabatic switching of both the gate and bottom plate parasitic capacitances, allowing up to 3.15GHz switching frequency for aggressive scaling of the on-chip inductors and capacitors achieving 4.1W/mm^2 power density from a very compact 0.33mm^2 total chip area. Furthermore, the output power is delivered continuously by means of both magnetic and electric couplings, thus providing <1% output voltage ripple. The switch control signals are naturally provided by the self-oscillating nature of the converter, thus eliminating the area and power overhead of phase generator, level shifter and bootstrap auxiliary circuits. Finally, a duty cycling scheme improves the efficiency in light loads which remains close to the peak with less than 1% degradation from 0.003W/mm2 up to 2.1W/mm2 of output power density.