LT1073

1

Rev B

TYPICAL APPLICATION

FEATURES

DESCRIPTION

Micropower

DC/DC Converter

Adjustable and Fixed 5V, 12V

TheLT®1073isaversatilemicropowerDC/DCconverter.The

device requires only three external components to deliver

a fixed output of 5V or 12V. The very low minimum supply

voltage of 1V allows the use of the LT1073 in applications

wheretheprimarypowersourceisasinglecell.Anon-chip

auxiliary gain block can function as a low-battery detector

or linear post-regulator.

Average current drain of the LT1073-5 used as shown in

theTypicalApplicationcircuitbelowisjust135µAunloaded,

making it ideal for applications where long battery life is

important. The circuit shown can deliver 5V at 40mA from

an input as low as 1.25V and 5V at 10mA from a 1V input.

The device can easily be configured as a step-up or step-

downconverter,althoughformoststep-downapplications

or input sources greater than 3V, the LT1173 is recom-

mended. Switch current limiting is user-adjustable by

adding a single external resistor. Unique reverse-battery

protection circuitry limits reverse current to safe, non-

destructive levels at reverse supply voltages up to 1.6V.

APPLICATIONS

n

No Design Required

n

Operates at Supply Voltages from 1V to 30V

n

Consumes Only 95µA Supply Current

n

Works in Step-Up or Step-Down Mode

n

Only Three External Off-the-Shelf Components

Required

n

Low-Battery Detector Comparator On-Chip

n

User-Adjustable Current Limit

n

Internal 1A Power Switch

n

Fixed or Adjustable Output Voltage Versions

n

Space-Saving 8-Pin PDIP or SO-8 Package

n

Pagers

n

Cameras

n

Single-Cell to 5V Converters

n

Battery Backup Supplies

n

Laptop and Palmtop Computers

n

Cellular Telephones

n

Portable Instruments

n

4mA to 20mA Loop Powered Instruments

n

Hand-Held Inventory Computers

n

Battery-Powered α, β, and γ Particle Detectors

L

, LTC, and LT are registered trademarks of Linear Technology Corporation.

Single-Cell to 5V Converter

Single Alkaline “AA” Cell Operating

Hours vs DC Load Current

+

1N5818

5V

40mA

100µF

SANYO

0S-CON

1073 TA01

LT1073-5

ILIM

VIN

SW1

SENSE

SW2

GND

1

2

3

4

5

8

1.5V

AA CELL*

CADDELL-BURNS

7300-12

82µH

OPERATES WITH CELL VOLTAGE ≥1V

ADD 10µF DECOUPLING CAPACITOR IF

BATTERY IS MORE THAN 2" AWAY FROM LT1073

*

LOAD CURRENT (mA)

1

1000

100

10

1

10

100

LT1073 TA02

L = 180µH

L = 82µH