The Si9145 switchmode controller IC is ideally suited for high efficiency dc/dc converters in low input voltage systems. Operation is guaranteed down to 2.7 V, with a minimum start-up voltage of 3.0 V making the Si9145 ideal for use with NiCd, NMH, and lithium ion battery packs. A mode select pin allows the output driver polarity to be programmed allowing the device to function as a step-up or step-down converter.