_______________General Description

The MAX877/MAX878/MAX879 are pulse-skipping, step-

up/step-down DC-DC converters that provide a regulated

output from inputs both above and below the output. They

require only three external components—an inductor

(typically 22µH) and two filter capacitors.

The MAX877 delivers a regulated 5V output from 2.5V to

6.2V inputs. The MAX878 generates pin-selectable volt-

ages of 3.0V or 3.3V from 1.5V to 6.2V inputs. The MAX879

output can be adjusted from 2.5V to 6V via an external

resistor divider from 2.5V to 6.2V inputs.

A unique high-power, internal, synchronous rectifier design

(Active Rectifier™) enables the devices to regulate in a

switched linear mode if the input voltage is higher than the

desired output voltage. When the input voltage falls below

the output voltage, the MAX877/MAX878/MAX879 will

smoothly switch into a pulse-skipping boost mode and

step up from input voltages as low as 1V. In shutdown, the

active rectifier disconnects the output from the source. This

stops the current drain from input to output associated with

conventional step-up converters.

High-frequency operation (up to 300kHz) allows the use of

small surface-mount inductors. Supply current is 195µA

under no load, and only 20µA in shutdown mode. For 1-cell

(1V) step-up converters with similar performance and the

same pinout, refer to the MAX777/MAX778/MAX779 data

sheet.

________________________Applications

Two or Three NiCd Cells to 3V/3.3V Conversion

Three or Four Alkaline Cells to 5V Conversion

One Lithium Cell to 3V/3.3V Conversion

Pagers

Palmtop and Notebook Computers

Battery-Powered and Hand-Held Instruments

____________________________Features

o Regulates from Inputs Above & Below the Output

o 1V to 6.2V Supply-Voltage Range

o Internal 1A Active Rectifier with Input-to-Output

Disconnect in Shutdown

o Up to 210mA Load Currents, Guaranteed

o 85% Efficiency

o Only 3 External Components

o Adjustable Current Limit

o 195µA Quiescent Supply Current

o 20µA Shutdown Supply Current

o 3V/3.3V/5V and Adjustable Output Voltage Versions

o Available in 8-Pin DIP and SO Packages

______________Ordering Information

Ordering Information continued on last page.

* Contact factory for dice specifications.

5V/3.3V/3V/Adjustable-Output,

Step-Up/Step-Down DC-DC Converters

________________________________________________________________

Maxim Integrated Products

1

INPUT

1.8V TO 6.2V

IN

ILIM

SHDN

100µF

OUTPUT

3.3V

210mA

AGND

MAX878

LX

OUT

PGND

22µH

ON/OFF

22

µF

1

2

7

8

3

6

5

SEL

4

__________________Pin Configuration

1

2

3

4

DIP/SO

TOP VIEW

MAX877

MAX878

MAX879

8

7

6

5

SHDN

OUT

LX

ILIM

IN

AGND

PGND

__________Typical Operating Circuit

Call toll free 1-800-998-8800 for free samples or literature.

19-0204; Rev 1; 5/94

PART

TEMP. RANGE

PIN-PACKAGE

MAX877CPA

0°C to +70°C

8 Plastic DIP

MAX877CSA

0°C to +70°C

8 SO

MAX877C/D

0°C to +70°C

Dice*

MAX877ESA

-40°C to +85°C

8 SO

MAX877EPA

-40°C to +85°C

8 Plastic DIP

MAX877MJA

-55°C to +125°C

8 CERDIP

™ Active Rectifier is a trademark of Maxim Integrated Products.

EVALUATION

KIT MANUAL

FOLLOWS

DATA

SHEET