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