A 94.5% Peak Efficiency, 14mV Output Ripple SC-Buck Step-Up Converter with 1.2-to-5V Output Achieving 20.2% Enhanced Power Efficiency in New PMU Architecture for SoCs

Abstract

For SoC and IoT systems, conventional power management unit (PMU) uses Buck converter and LDOs. With the increase of load current consumed by the digital circuits, the overall efficiency of the conventional architecture deteriorates due to the drop-voltage of the LDO. A new PMU architecture is proposed in this paper to break through the bottleneck of efficiency. The LDO is removed and a step-up converter provides the high voltage for the analog domain. The supply efficiency of the whole SoC could be improved because no LDO is needed for the current-hungry digital circuits. The new step-up converter named switched capacitor Buck (SCB) converter is presented by adding the switched capacitor network in the Buck converter. The most notable feature of SCB converter is that it achieves the step-up conversion with the Buck-like mode. It means that the transfer function, loop design, output ripple, and other characteristics are almost same as Buck converter, which help the implementation of proposed PMU. A prototype is implemented with a standard 0.18-μm CMOS technology. The whole system achieves high power efficiency of 94.5% For the system's power supply efficiency of SoC, the proposed PMU improves the efficiency by at least 12.5% than that of the conventional scheme.