General Description

The MAX8553 is a 4.5V to 28V input-voltage, synchro-

nous step-down controller that provides a complete

power-management solution for DDR memory. The

VTTR. The VTT and VTTR tracking voltages are main-

28V input voltage, nontracking step-down controller with

a low 0.6V feedback threshold voltage. The MAX8553/

MAX8554 use Maxim’s proprietary Quick-PWM™ archi-

tecture for fast transient response and operate with

selectable pseudo-fixed frequencies. Both controllers

can operate without an external bias supply.

The controllers operate in synchronous-rectification mode

to ensure balanced current sourcing and sinking capabili-

ty of up to 25A. The MAX8553/MAX8554 also provide up

to 95% efficiency, making them ideal for server and point-

of-load applications. Additionally, a low 5µA shutdown

current allows for longer battery life in notebook applica-

tions. Lossless current monitoring is achieved by monitor-

ing the low-side MOSFET’s drain-to-source voltage. The

MAX8553/MAX8554 have an adjustable foldback current

limit to withstand a continuous output overload and short

circuit. Digital soft-start provides control of inrush current

during power-up. Overvoltage protection shuts the con-

verter down and discharges the output capacitor. The

MAX8553/MAX8554 come in space-saving 16-pin QSOP

packages.

Applications

Wide-Input Power Supplies

Servers and Storage Applications

ASIC and CPU Core Voltages

Notebook and LCD-PC Power Supplies

DDR I and DDR II Memory Power Supplies

AGTL Bus Termination Supplies

Features

o Up to 25A Output-Current Capability

o Quick-PWM Control for Fast Loop Response

o Up to 95% Efficiency

o 4.5V to 28V Input Voltage Range

o No External Bias Supply Required

o 0 to 3.6V Input REFIN Range (MAX8553)

o Automatically Sets VTT and VTTR to within ±1%

o Low 0.6V Feedback Threshold (MAX8554)

o 200kHz/300kHz/400kHz/550kHz Selectable

Switching Frequencies

o Adjustable Foldback Current Limit

o Overvoltage Protection

o Digital Soft-Start

4.5V to 28V Input, Synchronous PWM Buck Controllers

for DDR Termination and Point-of-Load Applications

________________________________________________________________ Maxim Integrated Products

1

Ordering Information

MAX8553

DH

EN/HSD

+5V

POK

VIN

VOUT

VTTR

V+

REFIN

LX

DL

VTTR

GND

POK

REFIN

VL

BST

V+

REF

ILIM

FSEL

PGND

VTT

PART

TEMP RANGE

PIN-PACKAGE

MAX8553EEE

-40

°C to +85°C

16 QSOP

MAX8554EEE

-40

°C to +85°C

16 QSOP

Typical Operating Circuit

19-3017; Rev 0; 10/03

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.

Pin Configurations appear at end of data sheet.

Quick-PWM is a trademark of Maxim Integrated Products, Inc.