A single-inductor 7+7 ratio reconfigurable resonant switched-capacitor DC-DC converter with 0.1-to-1.5V output voltage range

Abstract

This paper demonstrates the first 7-ratio resonant switched capacitor (SC) converter using only a single inductor, realizing the widest resonant operating range reported in CMOS. A frequency-scaled gear train SC topology is introduced that enables soft-charging of all flying capacitors through one inductor at any arbitrary binary ratio by eliminating the inter-stage decoupling required in prior-art. Gear ratio modulation is proposed to control the resonance Q-factor, and hence the regulator can be gracefully transitioned from a resonant converter to a fully-capacitive SC, enabling > 24,000x output current range. For the same footprint, the converter achieves up to 14.4% and 12% efficiency improvements over co-fabricated SC and 3-level buck converters, respectively, while operating with a peak efficiency of 73.3% and current density of 0.14 A/mm2 in 0.18 μm bulk.