General Description

The MAX1857 low-dropout linear regulator operates

from a +2.5V to +5.5V supply and delivers a guaran-

teed 500mA load current with low 120mV dropout. The

high-accuracy (±1%) output voltage is preset at an

internally trimmed 4.75V or can be adjusted from 1.25V

to 5.0V with an external resistive divider.

An internal PMOS pass transistor allows the low 135µA

supply current to remain independent of load, making

this device ideal for portable battery-operated equip-

ment such as personal digital assistants (PDAs), cellu-

lar phones, cordless phones, base stations, and

notebook computers.

Other features include an active-low open-drain reset

output with a 4.5ms timeout period that indicates when

the output is out of regulation, a 0.1µA shutdown mode,

short-circuit protection, and thermal shutdown protec-

tion. The device is available in a miniature 8-pin µMAX

package. For higher power applications, refer to the

MAX1792 and MAX1793 data sheets.

________________________Applications

Notebook Computers

Cellular and Cordless Telephones

PDAs

Palmtop Computers

Base Stations

USB Hubs

Docking Stations

Features

o Guaranteed 500mA Output Current

o Low 120mV Dropout at 500mA

o Up to ±1% Output Voltage Accuracy

Preset at 4.75V

Adjustable from 1.25V to 5.0V

o Reset Output with 4.5ms Timeout Period

o Low 135µA Ground Current

o 0.1µA Shutdown Current

o Thermal Overload Protection

o Output Current Limit

o Tiny µMAX Package

500mA, Low-Dropout,

Ripple-Rejecting LDO in µMAX

________________________________________________________________ Maxim Integrated Products

1

SET

GND

SHDN

1

2

8

7

OUT

OUT

IN

RST

IN

µMAX

TOP VIEW

3

4

6

5

MAX1857

Pin Configuration

NC

MAX1857

IN

IN

ON

OFF

1

µF

SHDN

OUT

OUT

RST

GND

SET

3.3

µF

TO

µC

100k

Typical Operating Circuit

19-1812; Rev 0; 1/01

Ordering Information

PART*

TEMP. RANGE

PIN-PACKAGE

MAX1857EUA47

-40

°C to +85°C

8

µMAX

*Contact factory for other preset output voltages.

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.