Single Inductor Dual Output Buck Converter for Low Power Applications and Its Stability Analysis

The applications like sensor nodes and wearables, which run on coin/button cell and/or harvested energy source need small form factor and very low power consumption. A single inductor multiple output (SIMO) converter provides saving on inductor count and hence becomes a right choice for such applications. This paper presents a single inductor dual output (SIDO) buck converter targeting light load applications. The architecture uses discontinuous conduction mode (DCM) with pulse frequency modulation (PFM) control and the switching scheme ensures almost zero cross-regulation. The proposed converter is simulated in 180 nm CMOS technology showing zero cross-regulation. An efficiency of above 88% is achieved considering inductor and package losses in load range of micro-amperes to a few milli-amperes. This paper also presents a detailed stability analysis and model for the selected SIMO architecture along with some interesting observations and inferences derived from this analysis.