General Description

The MAX8545/MAX8546/MAX8548 are voltage-mode

pulse-width-modulated (PWM), step-down DC-DC con-

trollers ideal for a variety of cost-sensitive applications.

They drive low-cost n-channel MOSFETs for both the

high-side switch and synchronous rectifier, and require

no external current-sense resistor. These devices can

supply output voltages as low as 0.8V.

The MAX8545/MAX8546/MAX8548 have a wide 2.7V to

28V input range, and do not need any additional bias

voltage. The output voltage can be precisely regulated

ciency up to 95%. Lossless short-circuit and current-limit

low-side MOSFET. The MAX8545 and MAX8548 have a

current-limit threshold of 320mV, while the MAX8546 has

a current-limit threshold of 165mV. All devices feature

foldback-current capability to minimize power dissipation

under short-circuit condition. Pulling the COMP/EN pin

low with an open-collector or low-capacitance, open-

drain device can shut down all devices.

The MAX8545/MAX8546 operate at 300kHz and the

MAX8548 operates at 100kHz. The MAX8545/MAX8546/

MAX8548 are compatible with low-cost aluminum elec-

trolytic capacitors. Input undervoltage lockout prevents

proper operation under power-sag operations to prevent

external MOSFETs from overheating. Internal soft-start is

included to reduce inrush current. These devices are

Applications

Features

♦ 2.7V to 28V Input Range

♦ Foldback Short-Circuit Protection

♦ No Additional Bias Supply Needed

♦ Up to 95% Efficiency

♦ Low-Cost External Components

♦ No Current-Sense Resistor

♦ All n-Channel MOSFET Design

♦ Adaptive Gate Drivers Eliminate Shoot-Through

♦ Lossless Overcurrent and Short-Circuit

Protection

♦ 300kHz Switching Frequency

(MAX8545/MAX8546)

♦ 100kHz Switching Frequency (MAX8548)

♦ Pin-Compatible with the MAX1967

♦ Thermal Shutdown

Low-Cost, Wide Input Range, Step-Down

Controllers with Foldback Current Limit

________________________________________________________________ Maxim Integrated Products

1

MAX8545

MAX8546

MAX8548

ON

OFF

OPTIONAL

BST

COMP/

EN

VL

DH

LX

DL

GND

FB

INPUT

2.7V TO 28V

OUTPUT

0.8V TO

UP TO 6A

Typical Operating Circuit

Ordering Information

Pin Configuration appears at end of data sheet.

19-2795; Rev 2; 6/07

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

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

PART

TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX8545EUB

-40°C to +85°C

10 µMAX

U10-2

MAX8545EUB+

-40°C to +85°C

10 µMAX

U10-2

MAX8546EUB

-40°C to +85°C

10 µMAX

U10-2

MAX8546EUB+

-40°C to +85°C

10 µMAX

U10-2

MAX8548EUB

-40°C to +85°C

10 µMAX

U10-2

MAX8548EUB+

-40°C to +85°C

10 µMAX

U10-2

Selector Guide

PART

SWITCHING

FREQUENCY

(kHz)

CURRENT-LIMIT

THRESHOLD

(mV)

MAX8545

300

-320

MAX8546

300

-165

MAX8548

100

-320

Set-Top Boxes

Graphic Card and Video

Supplies

Desktops and Desknotes

PCI Express Power

Supplies

Telecom Power Supplies

Notebook Docking

Station Supplies

Cable Modems and

Routers

Networking Power

Supplies

+Denotes a lead-free package.

µMAX is a registered trademark of Maxim Integrated Products, Inc.