General Description

The MAX1733/MAX1734 step-down DC-DC converters

deliver over 250mA to outputs as low as 1.25V. These

converters use a unique proprietary current-limited con-

trol scheme that achieves over 90% efficiency. These

devices maintain extremely low quiescent supply cur-

rent (40µA), and their high 1.2MHz (max) operating fre-

quency permits small, low-cost external components.

This combination of features makes the MAX1733/

MAX1734 excellent high-efficiency alternatives to linear

regulators in space-constrained applications.

Internal synchronous rectification greatly improves effi-

ciency and eliminates the external Schottky diode

required in conventional step-down converters. Both

devices also include internal digital soft-start to limit

input current upon startup and reduce input capacitor

requirements.

The MAX1733 provides an adjustable output voltage

(1.25V to 2.0V). The MAX1734 provides factory-preset

output voltages (see Selector Guide). Both are avail-

able in space-saving 5-pin SOT23 packages.

Applications

Cellular, PCS, and Cordless Telephones

PDAs, Palmtops, and Handy-Terminals

Battery-Powered Equipment

Features

o 250mA Guaranteed Output Current

o Synchronous Rectifier for Over 90% Efficiency

o Tiny 5-Pin SOT23 Package

o 40µA Quiescent Supply Current

o 0.01µA Logic-Controlled Shutdown

o Up to 1.2MHz Switching Frequency

o Fixed 1.8V or 1.5V Outputs (MAX1734)

o Adjustable Output Voltage (MAX1733)

o ±1.5% Initial Accuracy

o 2.7V to 5.5V Input Range

o Soft-Start Limits Startup Current

Low-Voltage, Step-Down DC-DC Converters

in SOT23

________________________________________________________________ Maxim Integrated Products

1

GND

OUT (FB)

( ) ARE FOR MAX1733 ONLY.

SHDN

15

LX

IN

MAX1733

MAX1734

SOT23-5

TOP VIEW

2

34

Pin Configuration

OUT

250mA

INPUT

+2.7V TO +5.5V

LX

IN

MAX1734

SHDN

GND

10

µH

22

µF

2.2

µF

Typical Operating Circuit

19-1586; Rev 0; 7/00

For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.

For small orders, phone 1-800-835-8769.

Note: The MAX1734 offers two output voltages. See the Selector

Guide, then insert the proper designator into the blanks above to

complete the part number.

Ordering Information

PART

TEMP. RANGE

PIN-PACKAGE

MAX1733EUK-T

-40

°C to +85°C

5 SOT23-5

MAX1734EUK_ _-T

-40

°C to +85°C

5 SOT23-5

Selector Guide

PART

TOP MARK

MAX1733EUK

Adjustable

ADKY

MAX1734EUK18

1.8

ADKW

MAX1734EUK15

1.5

ADKX