General Description

The MAX887 high-efficiency, step-down DC-DC converter provides an adjustable output from 1.25V to 10.5V. It accepts inputs from 3.5V to 11V and delivers 600mA. Operation to 100% duty cycle minimizes dropout voltage (300mV typ at 500mA). Synchronous rectification reduces output rectifier losses, resulting in efficiency as high as 95%.

Fixed-frequency pulse-width modulation (PWM) reduces noise in sensitive communications applications. Using a high-frequency internal oscillator allows tiny surface-mount components to reduce PC board area, and eliminates audio-frequency interference. A SYNC input allows synchronization to an external clock to avoid interference with sensitive RF and data acquisition circuits.

Features

♦ 95% Efficiency

♦ 600mA Output Current

♦ Cycle-by-Cycle Current Limiting

♦ Low-Dropout, 100% Duty-Cycle Operation, 300mV at 500mA

♦ Internal 0.6Ω (typ) MOSFET

♦ Internal Synchronous Rectifier

♦ High-Frequency Current-Mode PWM

♦ External SYNC or Internal 300kHz Oscillator

♦ Guaranteed 260kHz to 340kHz Internal Oscillator Frequency Limits

♦ 2.5µA Shutdown Mode

Applications

  Portable Instruments

  Cellular Phones and Radios

  Personal Communicators

  Distributed Power Systems

  Computer Peripherals