The MAX1800 provides a complete power-supply solution for digital still cameras and video cameras. The device integrates a high-efficiency main step-up DC-DC converter, three auxiliary step-up controllers, and an uncommitted gain block that drives an external P-channel MOSFET for a linear regulator. The MAX1800 is targeted for applications that use either two or three primary cells or a single lithium-ion (Li+) battery. The main DC-DC converter accepts inputs from +0.7V to +5.5V and regulates a resistor-adjustable output from 2.7V to 5.5V. It uses an internal synchronous rectifier to regulate the output with 95% efficiency. An adjustable operating frequency facilitates designs for optimum size, cost, and efficiency.