_______________General Description

The MAX649/MAX651/MAX652 BiCMOS, step-down DC-

DC switching controllers provide high efficiency over

three decades of load current. A unique, current-limited

pulse-frequency-modulated (PFM) control scheme gives

these devices the benefits of pulse-width-modulation

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

using only 100µA of supply current (vs. 2mA to 10mA for

PWM converters). The result is high efficiency over loads

ranging from 10mA to more than 2.5A.

These devices use miniature external components.

Their high switching frequency (up to 300kHz) allows

for less than 9mm diameter surface-mount inductors.

The MAX649/MAX651/MAX652 have dropout voltages

less than 1V and accept input voltages up to 16.5V.

Output voltages are preset at 5V (MAX649), 3.3V

(MAX651), and 3V (MAX652). These controllers can

also be adjusted to any voltage from 1.5V to the input

voltage by using two resistors.

These step-down controllers drive external P-channel

MOSFETs at loads greater than 10W. If less power is

required, use the MAX639/MAX640/MAX653 step-down

converters with on-chip FETs, which allow up to a

225mA load current.

________________________Applications

5V-to-3.3V Green PC Applications

High-Efficiency Step-Down Regulation

Minimum-Component DC-DC Converters

Battery-Powered Applications

____________________________Features

o More than 90% Efficiency (10mA to 1.5A Loads)

o More than 12.5W Output Power

o 100µA Max Quiescent Supply Current

o 5µA Max Shutdown Supply Current

o Less than 1.0V Dropout Voltage

o 16.5V Max Input Voltage

o 5V (MAX649), 3.3V (MAX651), 3V (MAX652),

or Adjustable Output Voltage

o Current-Limited Control Scheme

o Up to 300kHz Switching Frequency

______________Ordering Information

Ordering Information continued at end of data sheet.

**Contact factory for availability and processing to MIL-STD-883.

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

________________________________________________________________

Maxim Integrated Products

1

1

2

3

4

8

7

6

5

GND

EXT

CS

V+

REF

SHDN

FB

OUT

DIP/SO

TOP VIEW

MAX649

MAX651

MAX652

__________________Pin Configuration

__________Typical Operating Circuit

19-0225; Rev 3; 9/97

PART

TEMP. RANGE

PIN-PACKAGE

MAX649CPA

0°C to +70°C

8 Plastic DIP

MAX649CSA

0°C to +70°C

8 SO

MAX649C/D

0°C to +70°C

Dice*

MAX649EPA

-40°C to +85°C

8 Plastic DIP

MAX649ESA

-40°C to +85°C

8 SO

MAX649MJA

-55°C to +125°C

8 CERDIP**

MAX651

V+

CS

SHDN

FB

GND

ON/OFF

P

EXT

REF

OUT

OUTPUT

3.3V

INPUT

4V TO 16.5V

EVALUATION

KIT

AVAILABLE

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

For small orders, phone 1-800-835-8769.