General Description

The MAX687/MAX688/MAX689 low-dropout linear regulators operate with an input-to-output voltage differential limited only by an external PNP transistor. Outputs are fixed at 3.3V (MAX687/MAX688) or 3.0V (MAX689). The only external components required are a PNP pass transistor and output, compensation, and bypass capacitors. Base drive to the external transistor is at least 10mA, permitting output currents to exceed 1A when using high-gain transistors (β > 100). Output current limiting is implemented by limiting the external transistor’s base current. Output voltage monitoring and shutdown functions are included.

Features

♦ Fixed Outputs:

   3.3V (MAX687/MAX688)

   3.0V (MAX689)

♦ Directly Drives External PNP Transistor

♦ 10mA Min Base-Current Drive for >1A Output

♦ Low Dropout Voltage:

   100mV Dropout at 650mA Output (FZT749)

   40mV Dropout at 200mA Output (FZT749)

   0.8V Dropout at 4A Output

♦ Power-Fail Output Monitors the Output Voltage

♦ Automatic, Latched Shutdown when Output Falls Out

   of Regulation (MAX687)

♦ Precision Threshold Shutdown Control

   (MAX688/MAX689)

♦ Low Supply Current:

   150µA Operating

   <1µA Shutdown

♦ 2.7V to 11.0V Supply Range

♦ 8-Pin DIP/SO/µMAX Packages

♦ <2mV Line Transient with 3.4V to 3.6V Input

♦ Output Accuracy

Applications

   High-Efficiency Linear Regulator

   Battery-Powered Devices

   Portable Instruments

   Portable Telephones

   Power Supply or Backup Supply for Memory