General Description

The MAX1973/MAX1974 are constant-frequency

1.4MHz pulse-width-modulated (PWM) current-mode

step-down regulators. The output voltage can be set as

low as 0.75V using an external voltage-divider, or it can

be set to preset outputs of 1V, 1.5V (MAX1974), 1.8V,

or 2.5V (MAX1973) without requiring external resistors.

The MAX1973 also includes a voltage-margining fea-

ture that offsets the output voltage up or down 4% to

facilitate board-level production testing.

A fixed 1.4MHz operating frequency ensures operation

outside the DSL frequency band, provides fast transient

response, and allows the use of small external compo-

nents. Only 4.7µF input and output ceramic capacitors

are needed for 1A applications. Forced PWM operation

ensures a constant switching frequency over all load

conditions.

Output voltage accuracy is ±1% over load, line, and

temperature operating ranges. The MAX1973 features

voltage margining; the MAX1974 provides a POK out-

put to indicate when the output has reached 90% of its

nominal regulation voltage. Both devices are available

in small 10-pin µMAX packages.

Applications

Network Equipment

Cellular Base Stations

DSL and Wireless Modems/Routers

Optical Modules

Central-Office DSL and Telecom

DSP/ASIC Core and IO supplies

Features

o Ultra-Low Circuit Height of 1.8mm

o 4.7µF Ceramic Input and Output Capacitors

o 2.6V to 5.5V Input Voltage

o 1A Output Current

o 1% Accurate

o Built-In ±4% Logic-Controlled Voltage Margining

(MAX1973)

Adjustable Output

o Fixed-Frequency PWM Current-Mode Operation

o 1.4MHz Switching Frequency, Operate Outside

DSL Band

o 100% Duty-Cycle Dropout Capability

o Small External Components

Smallest 1A, 1.4MHz Step-Down Regulators

________________________________________________________________ Maxim Integrated Products

1

1

2

3

4

5

10

9

8

7

6

CTL1

IN

LX

PGND

SS

FB

COMP

FBSEL

MAX1973

µMAX

TOP VIEW

CTL2

GND

1

2

3

4

5

10

9

8

7

6

ON

IN

LX

PGND

SS

FB

COMP

FBSEL

MAX1974

µMAX

POK

GND

Pin Configurations

Ordering Information

MAX1973

IN

COMP

FBSEL

SS

GND

LX

FB

CTL1

CTL2

PGND

INPUT

2.6V TO 5.5V

MAX1974 OUTPUT DOWN TO 0.75V

VOLTAGE

MARGINING

ON/OFF

OUTPUT

1A

Typical Operating Circuit

19-2547; Rev 0; 7/02

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

MAX1973EUB

-40

°C to +85°C

10 µMAX

MAX1974EUB

-40

°C to +85°C

10 µMAX

Selector Guide appears at end of data sheet.