A multi-output on-chip switched-capacitor DC-DC converter for near- and sub-threshold power modes

This paper presents a novel multi-output on-chip switched-capacitor (SC) DC-DC converter simultaneously providing two output voltages (2VDD/3 and VDD/3, in addition to the available full VDD) that enables the use of three different power modes for optimizing power/performance trade-offs: super-threshold (full VDD), near-threshold (2VDD/3) and sub-threshold (VDD/3). Unlike previously proposed SC converters, the multiple conversion ratios of the novel converter are achieved without changing the topology of the circuit, thus fewer components being needed to support multiple voltages. Above 84% and 70% efficiencies are obtained in simulation over a range of load currents from 0.4 mA to 5 mA, and from 0.4 mA to 1 mA, with conversion ratios of 2/3 and 1/3, respectively. The paper also presents a novel optimization method to save area by using unequally sized flying capacitors. The target application is for systems with discrete power modes; also for systems that use dithering to emulate a continuous range of voltages such as the Panoptic Dynamic Voltage Scaling (PDVS).