________________________________________________________________

Maxim Integrated Products

1

_______________General Description

The MAX639/MAX640/MAX653 step-down switching

regulators provide high efficiency over a wide range of

load currents, delivering up to 225mA. A current-limiting

pulse-frequency-modulated (PFM) control scheme gives

the devices the benefits of pulse-width-modulated

(PWM) converters (high efficiency at heavy loads), while

using only 10µA of supply current (vs. 2mA to 10mA for

PWM converters). The result is high efficiency over a

wide range of loads.

The MAX639/MAX640/MAX653 input range is 4V to

11.5V, and the devices provide lower preset output volt-

ages of 5V, 3.3V, and 3V, respectively. Or, the output

can be user-adjusted to any voltage from 1.3V to the

input voltage.

The MAX639/MAX640/MAX653 have an internal 1A power

MOSFET switch, making them ideal for minimum-compo-

nent, low- and medium-power applications. For increased

output drive capability, use the MAX649/MAX651/MAX652

step-down controllers, which drive an external P-channel

FET to deliver up to 5W.

________________________Applications

9V Battery to 5V, 3.3V, or 3V Conversion

High-Efficiency Linear Regulator Replacement

Portable Instruments and Handy-Terminals

5V-to-3.3V Converters

____________________________Features

o High Efficiency for a Wide Range of Load Currents

o 10µA Quiescent Current

o Output Currents Up to 225mA

o Preset or Adjustable Output Voltage:

5.0V (MAX639)

3.3V (MAX640)

3.0V (MAX653)

o Low-Battery Detection Comparator

o Current-Limiting PFM Control Scheme

______________Ordering Information

Ordering Information continued on last page.

* Contact factory for dice specifications.

5V/3.3V/3V/Adjustable, High-Efficiency,

19-4505; Rev 3; 8/97

PART

TEMP. RANGE

PIN-PACKAGE

MAX639CPA

0°C to +70°C

8 Plastic DIP

MAX639CSA

0°C to +70°C

8 SO

MAX639C/D

0°C to +70°C

Dice*

1

2

3

4

5

8

7

6

MAX639

MAX640

MAX653

DIP/SO

TOP VIEW

VFB

SHDN

V+

LX

VOUT

LBO

LBI

GND

__________________Pin Configuration

GND

MAX639

SHDN

LX

VOUT

LBO

LOW-BATTERY

DETECTOR

OUTPUT

ON/OFF

LBI

LOW-BATTERY

DETECTOR

INPUT

OUTPUT

5V

225mA

INPUT

5.5V TO 11.5V

V+

VFB

__________Typical Operating Circuit

MAX639ESA

-40°C to +85°C

8 SO

MAX639EPA

-40°C to +85°C

8 Plastic DIP

MAX639MJA

-55°C to +125°C

8 CERDIP

EVALUATION

KIT

INFORMATION

INCLUDED

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 408-737-7600 ext. 3468.