The step-down DC-DC converter can operate directly from the battery or from the step-up output, providing boost-buck capability with a compound efficiency of up to 90%. Both devices include three PWM DC-DC controllers: the MAX1584 includes two step-up controllers and one step-down controller, while the MAX1585 includes one step-up controller, one inverting controller, and one step-down controller. All DC-DC channels operate at one fixed frequency--settable from 100kHz to 1MHz--to optimize size, cost, and efficiency. Other features include soft-start, power-OK outputs, and overload protection. The MAX1584/MAX1585 are available in space-saving, 32-pin thin QFN packages. An evaluation kit is available to expedite designs.