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 alu-

minum electrolytic capacitors. Input undervoltage lock-

out prevents proper operation under power-sag

operations to prevent external MOSFETs from overheat-

ing. Internal soft-start is included to reduce inrush cur-

rent. These devices are offered in space-saving 10-pin

µMAX packages.

Applications

Features

o 2.7V to 28V Input Range

o Foldback Short-Circuit Protection

o No Additional Bias Supply Needed

o Up to 95% Efficiency

o Low-Cost External Components

o No Current-Sense Resistor

o All N-Channel MOSFET Design

o Adaptive Gate Drivers Eliminate Shoot-Through

o Lossless Overcurrent and Short-Circuit

Protection

o 300kHz Switching Frequency

(MAX8545/MAX8546)

o 100kHz Switching Frequency (MAX8548)

o Pin-Compatible with the MAX1967

o 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 0; 7/03

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.

PART

TEMP RANGE

PIN-PACKAGE

MAX8545EUB

-40

°C to +85°C

10 µMAX

MAX8546EUB

-40

°C to +85°C

10 µMAX

MAX8548EUB

-40

°C to +85°C

10 µMAX

Selector Guide

PART

SWITCHING

FREQUENCY

CURRENT-LIMIT

THRESHOLD

MAX8545

300kHz

-320mV

MAX8546

300kHz

-165mV

MAX8548

100kHz

-320mV

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