Dual-Output Step-Down DC-DC Converter for PDA/Palmtop Computers

The MAX1775 dual, step-down DC-DC converter generates both the main (+3.3V at over 2A) and core (+1.8V at up to 1.5A) supplies for a complete power solution for PDAs, subnotebooks, and other hand-held devices. The main output is adjustable from +1.25V to +5.5V. The core output is adjustable from 1V to 5V. Both switching converters operate at up to 1.25MHz for small external components and use synchronous rectifiers to achieve efficiencies up to 95%. Operation with up to 100% duty cycle provides the lowest possible dropout voltage to extend useful battery life.

The MAX1775 accepts inputs from +2.7V up to +28V, allowing use with many popular battery configurations as well as AC-DC wall adapters. Digital soft-start reduces battery current surges at power-up. Both the main and core converters have separate shutdown inputs. The MAX1775 comes in a small 16-pin QSOP package.

The MAX1775 evaluation kit is available to help reduce design time.

Applications

* Handheld Computers * Internet Access Tablets * PDAs * POS Terminals * Subnotebooks

* Dual, High-Efficiency, Synchronous Rectified Step-Down Converter

* Main Power

* Adjustable from +1.25V to +5.5V

* Over 2A Load Current

* Up to 95% Efficiency

* Core Power

* Adjustable from 1V to 5V

* Internal Switches

* Up to 1.5A Load Current

* Up to 92% Efficiency

* 100% (max) Duty Cycle

* Up to 1.25MHz Switching Frequency

* Input Voltage Range from +2.7V to +28V

* 170µA Quiescent Current

* 5µA Shutdown Current

* Digital Soft-Start

* Independent Shutdown Inputs