11.2 A 12V-to-1V Quad-Output Switched-Capacitor Buck Converter with Shared DC Capacitors Achieving 90.4% Peak Efficiency and 48mA/mm3 Power Density at 85% Efficiency

Abstract

Direct 12V-to-1 V power delivery has become popular in datacenter applications. Multiple outputs regulated by switching regulators are favorable to reduce the energy overhead. For example, from Fig. 11.2.1, a DDR5 dual in-line memory module (DIMM) requires multiple 1.1 V and 1.8V for core, I/O and word line boost supplies, each has several amperes of peak current. Single-inductor-multi-output (SIMO) design may be a low-cost solution, but it has a low efficiency and cross regulation. A widely used scheme is to supply each output with an independent converter [1]. For the 12V-to-1 V application, the conventional buck converter has a high switching loss. This leads to a low switching frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{f}_{\text{SW}}$</tex> ,, and hence a large inductor and low power density. Hybrid converters, such as multi-level converters [2], reduce the voltage stress of switches, and thus can use low-voltage devices with a better figure of merit (FoM). Yet, a large conduction loss takes place due to the stacked low-side (LS) switches, especially when these switches conduct most inductor current in 12V-to-1 V applications. As a result, large switches (area) are necessary to reduce the conduction loss. The dual-inductor hybrid (DIH) converters [3–5] have no stacked LS switches, but using a single inductor is preferable under several-amperes of load current.