_______________General Description

The MAX629 low-power DC-DC converter features an

internal N-channel MOSFET switch and programmable

current limiting. It is designed to supply positive or neg-

ative bias voltages up to ±28V from input voltages in

boost, flyback, and SEPIC topologies.

The MAX629’s current-limited pulse-frequency-modula-

tion (PFM) control scheme provides high efficiency over

a wide range of load conditions. An internal, 0.5A N-

channel MOSFET switch reduces the total part count,

and a high switching frequency (up to 300kHz) allows

for tiny surface-mount magnetics.

The MAX629’s combination of low supply current, logic-

controlled shutdown, small package, and tiny external

components makes it an extremely compact and effi-

cient high-voltage biasing solution that’s ideal for bat-

tery-powered applications. The MAX629 is available in

an 8-pin SO package.

________________________Applications

Positive or Negative LCD Bias Generators

High-Efficiency DC-DC Boost Converters

Varactor Tuning Diode Bias

Palmtop Computers

2-Cell and 3-Cell Battery-Powered Applications

____________________________Features

o Internal, 500mA, 28V N-Channel Switch

(No External FET Required)

o Generates Positive or Negative Output Voltages

o 80µA Supply Current

o 1µA Max Shutdown Current

o Up to 300kHz Switching Frequency

o Adjustable Current Limit Allows Use of Small,

Inexpensive Inductors

o 8-Pin SO Package

28V, Low-Power, High-Voltage,

Boost or Inverting DC-DC Converter

________________________________________________________________

Maxim Integrated Products

1

MAX629

SHDN

+2.7V

TO +5.5V

LX

GND

FB

ISET

POL

REF

POSITIVE OUTPUT VOLTAGE

MAX629

SHDN

-28V

28V

+2.7V

TO +5.5V

LX

GND

FB

REF

POL

NEGATIVE OUTPUT VOLTAGE

ISET

___________________________________________________Typical Operating Circuit

19-1219; Rev 1; 6/97

PART

TEMP. RANGE

PIN-PACKAGE

______________Ordering Information

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

Note: To order tape-and-reel shipping, add “-T” to the end of

the part number.

*

Pin Configuration appears at end of data sheet.

MAX629C/D

0°C to +70°C

Dice*

MAX629ESA

-40°C to +85°C

8 SO

EVALUATION

KIT MANUAL

AVAILABLE