A 47 MHz Hybrid Resonant SC Converter with Digital Switch Conductance Regulation and Multi-Mode Control for Li-Ion Battery Applications

A hybrid resonant DC-DC converter IC is introduced. It combines a three-ratio switched capacitor array with an inductor to efficiently convert a Li-Ion battery voltage of 3.0 V - 4.5 V into typically 1.8 V over a wide load range from 0.5 mA - 120 mA. The converter comprises two control options, both implemented by a fast mixed-signal controller. Switch conductance regulation (SwCR) operates up at resonance frequencies as large as 47 MHz, which offers full integration of passives on IC-level (no external components). In contrast, resonant bursting with dynamic off-time modulation (DOTM) achieves higher efficiency at the cost of an external output capacitor. The light load case down to currents as low as 0.5 mA is supported by automatic transition into pure non-resonant SC mode, controlled by frequency modulation. Experimental results for the fully integrated option (SwCR and SC mode) confirm 85% peak efciency with a total flying capacitance of 2 nF, a 9 nH spiral inductance and 10 nF output capacitance. Fast transient response settling of <250 ns is achieved with a small output voltage drop of 5.5 %. With an external 10nH inductance and 100 nF output capacitance (DOTM), 89% peak efficiency is achieved at negligible voltage droop (∆V
out
< 1 %).