General Description

The MAX1844 pulse-width modulation (PWM) controller

provides high efficiency, excellent transient response,

and high DC output accuracy needed for stepping

down high-voltage batteries to generate low-voltage

CPU core or chipset/RAM supplies in notebook com-

puters.

Maxim’s proprietary Quick-PWM™ quick-response,

constant-on-time PWM control scheme handles wide

input/output voltage ratios with ease and provides

100ns “instant-on” response to load transients while

maintaining a relatively constant switching frequency.

Efficiency is enhanced by an ability to drive very large

synchronous-rectifier MOSFETs. Accurate current sens-

ing to ensure reliable overload protection is available

using an external current-sense resistor in series with

the synchronous rectifier. Alternatively, the synchronous

rectifier itself can be used for less accurate current

sensing at the lowest possible power dissipation.

Single-stage buck conversion allows the MAX1844 to

directly step down high-voltage batteries for the highest

possible efficiency. Alternatively, two-stage conversion

(stepping down the 5V system supply instead of the

battery) at a higher switching frequency allows the mini-

mum possible physical size.

The MAX1844 is intended for CPU core, chipset,

DRAM, or other low-voltage supplies as low as 1V. It is

available in 20-pin QSOP, and QFN packages and

includes both adjustable overvoltage and undervoltage

protection.

For a dual step-down PWM controller with accurate cur-

rent limit, refer to the MAX1845. The MAX1714/ MAX1715

single/dual PWM controllers are similar to the MAX1844/

MAX1845 but do not use current-sense resistors.

Applications

Notebook Computers

CPU Core Supplies

Chipset/RAM Supplies as Low as 1V

1.8V and 2.5V Supplies

Features

o Ultra-High Efficiency

o Accurate Current-Limit Option

o Quick-PWM with 100ns Load-Step Response

o 1.8V/2.5V Fixed or 1V to 5.5V Adjustable Output

Range

o 2V to 28V Battery Input Range

o 200/300/450/600kHz Switching Frequency

o Adjustable Overvoltage Protection

o Adjustable Undervoltage Protection

o 1.7ms Digital Soft-Start

o Drives Large Synchronous-Rectifier FETs

o 2V ±1% Reference Output

o Power-Good Window Comparator

High-Speed Step-Down Controller with

Accurate Current Limit for Notebook Computers

________________________________________________________________ Maxim Integrated Products

1

19-1993; Rev 3; 9/02

EVALUATION

KIT

AVAILABLE

Pin Configuration appears at end of data sheet.

*Contact factory for availability.

Quick-PWM is a trademark of Maxim Integrated Products.

5V INPUT

BATTERY

4.5V TO 28V

OUTPUT

2.5V

SHDN

ILIM

DL

LX

V+

BST

DH

CS

OUT

SKIP

MAX1844

UVP

REF

PGOOD

LATCH

OVP

FB

GND

Minimal Operating Circuit

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

PART

TEMP RANGE

PIN-PACKAGE

MAX1844EEP

-40°C to +85°C

20 QSOP

MAX1844EGP*

-40°C to +85°C

20 QFN

MAX1844ETP

-40°C to +85°C

20 Thin QFN