A cross-regulation-free triple-output switched-capacitor DC-DC regulator for energy-harvesting applications

This paper presents a cross-regulation-free switched-capacitor (SC) DC-DC regulator that is able to simultaneously produce three different regulated output voltages for energy harvesting applications. With capacitor and power switch sharing, the proposed power stage can realize separate 2x, 3x and 4x outputs, while saving 3 flying capacitors and 9 power switches compared with using an independent single-output doubler, tripler and quadrupler. A sub-harmonic fixed on-time control scheme is developed not only to regulate all outputs, but also to improve the light-load regulator power efficiency, minimize cross-regulations between the three outputs, and provide predictable noise spectrum of all regulated outputs. Implemented in a standard 0.35μm CMOS process, the proposed regulator can provide three regulated outputs of 2V, 3V and 4V under 1.1V input voltage, and deliver up to 15mA (2V), 12mA (3V), 2mA (4V) local currents. The proposed regulator also achieves a maximum power efficiency of 89.8%.