3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

________________________________________________________________

Maxim Integrated Products

1

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

19-0113; Rev. 2; 1/95

_______________General Description

The MAX756/MAX757 are CMOS step-up DC-DC switch-

ing regulators for small, low input voltage or battery-pow-

ered systems. The MAX756 accepts a positive input

voltage down to 0.7V and converts it to a higher pin-

selectable output voltage of 3.3V or 5V. The MAX757 is

an adjustable version that accepts an input voltage down

to 0.7V and generates a higher adjustable output voltage

in the range from 2.7V to 5.5V. Typical full-load efficiencies

for the MAX756/MAX757 are greater than 87%.

The MAX756/MAX757 provide three improvements over

previous devices. Physical size is reduced—the high

switching frequencies (up to 0.5MHz) made possible by

MOSFET power transistors allow for tiny (<5mm diameter)

surface-mount magnetics. Efficiency is improved to 87%

(10% better than with low-voltage regulators fabricated in

bipolar technology). Supply current is reduced to 60µA

by CMOS construction and a unique constant-off-time

pulse-frequency modulation control scheme.

________________________Applications

3.3V to 5V Step-Up Conversion

Palmtop Computers

Portable Data-Collection Equipment

Personal Data Communicators/Computers

Medical Instrumentation

2-Cell & 3-Cell Battery-Operated Equipment

Glucose Meters

____________________________Features

o Operates Down to 0.7V Input Supply Voltage

o 87% Efficiency at 200mA

o 60µA Quiescent Current

o 20µA Shutdown Mode with Active Reference and

LBI Detector

o 500kHz Maximum Switching Frequency

o ±1.5% Reference Tolerance Over Temperature

o Low-Battery Detector (LBI/LBO)

o 8-Pin DIP and SO Packages

______________Ordering Information

1

2

3

4

8

7

6

5

LX

GND

OUT

LBI

LBO

REF

3/5

SHDN

MAX756

DIP/SO

TOP VIEW

1

2

3

4

8

7

6

5

LX

GND

OUT

LBI

LBO

REF

FB

SHDN

MAX757

DIP/SO

_________________Pin Configurations

MAX756

SHDN

1

3/5

2

REF

3

LBI

5

LX

7

150

µF

GND

OUT

6

INPUT

1N5817

OUTPUT

5V at 200mA

or

3.3V at 300mA

100

µF

LBO

4

8

0.1

µF

22

µH

LOW-BATTERY

DETECTOR OUTPUT

__________Typical Operating Circuit

PART

TEMP. RANGE

PIN-PACKAGE

MAX756CPA

0°C to +70°C

8 Plastic DIP

MAX756CSA

0°C to +70°C

8 SO

MAX756C/D

0°C to +70°C

Dice*

MAX756EPA

-40°C to +85°C

8 Plastic DIP

MAX756ESA

-40°C to +85°C

8 SO

MAX757CPA

0°C to +70°C

8 Plastic DIP

MAX757CSA

0°C to +70°C

8 SO

MAX757C/D

0°C to +70°C

Dice*

MAX757EPA

-40°C to +85°C

8 Plastic DIP

MAX757ESA

-40°C to +85°C

8 SO

EVALUATION

KIT MANUAL

FOLLOWS

DATA

SHEET