This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for providing positive and negative voltages of a power supply. In one aspect, the power supply includes an inductor having a first end coupled via a source switch to a voltage source and coupled via a first plurality of output switches to a respective plurality of negative outputs and a second end coupled via a ground switch to a ground potential and coupled via a second plurality of output switches to a respective plurality of positive outputs and a controller adapted to configure the switches into at least one of multiple configurations.