A Multi-Output on-Chip Switched-Capacitor DC-DC Converter with Unequal Flying Capacitors for Different Power Modes

This paper presents a multi-output on-chip switched-capacitor (SC) DC-DC converter simultaneously providing two output voltages (2V(DD)/3 and V-DD/3, in addition to the available full V-DD) that enables the use of three different power modes for optimizing system power/performance trade-offs: super-threshold (full V-DD), near-threshold (2V(DD)/3) and sub-threshold (V-DD/3). Unlike some previously proposed multi-output SC converters, the multiple conversion ratios of the proposed converter are achieved without changing the topology of the circuit, thus fewer components being needed to support multiple voltages. The paper also presents an optimization method by using unequal flying capacitors for different regions of the circuit by taking advantage of the different levels of expected power consumption in the various power modes. Above 84% and 70% effciencies are obtained in simulation over a range of load currents from 0.4 to 5 mA, and from 0.4 to 1 mA, with conversion ratios of 2/3 and 1/3, respectively. The target application for the proposed converter is for circuits with discrete power modes and for systems that use dithering to emulate a continuous range of voltages such as the panoptic dynamic voltage scaling (PDVS).