A 45-ratio recursively sliced series-parallel switched-capacitor DC-DC converter achieving 86% efficiency

A Recursive Ternary switched-capacitor (RT-SC) topology that achieves more than 3(3^N-1)/2 ratios with N SC cells is presented. To achieve the high number of ratios for a wide output voltage range, a three-ratio (1/3, 1/2, 2/3) Series-Parallel (SP) topology is sliced into N reconfigurable three-ratio SP sub-cells that are interconnected in a series or stacked configuration in order to realize a minimum voltage-conversion resolution of V_in/6^N. Importantly, this modular approach supports a recursively defined topology, by operating the three-ratio SP sub-cells in parallel the high efficiency at large power density of a standard three-ratio SP converter is achieved. The proposed RT-SC converter realizes ternary m₃/3^N conversion ratios as well as binary m₂/2^N and mixing m₆/6^N-1 modes. A 45-ratio fully-integrated RT-SC is fabricated in a 0.25 μm CMOS process, achieving 53% larger output operating range than a conventional three-ratio SP at 0.5 mA/mm², and 15% higher efficiency than a Recursive Binary SC at 3.4× larger current density.