Resonant-Switched Capacitor Converters for Chip-Scale Power Delivery: Design and Implementation

There is an increasing need for power management systems that can be fully integrated in silicon to reduce cost and form factor in mobile applications, and provide point-of-load voltage regulation for high-performance digital systems. Switched-capacitor (SC) converters have shown promise in this regard due to relatively high energy-density of capacitors and favorable device utilization figures of merit. Resonant switched-capacitor (ReSC) converters show similar promise as they benefit from many of the same architectures and scaling trends, but also from ongoing improvements in mm-scale magnetic devices. In this study, we explore the design and optimization of 2:1 step-down topologies, based on representative capacitor technologies, CMOS device parameters, and air-core inductor models. We compare the SC approach to the ReSC approach in terms of efficiency and power density. Finally, a chip-scale ReSC converter is presented that can deliver over 4 W at 0.6 W/mm² with 85% efficiency. The two-phase, nominally 2:1 converter supports input voltages from 3.6-6.0 V, and is implemented in 180-nm bulk CMOS with die-attached air-core solenoid inductors.