1

LT1521/LT1521-3

LT1521-3.3/LT1521-5

The LT

dropout regulators with micropower quiescent current

and shutdown. These devices are capable of supplying

300mA of output current with a dropout voltage of 0.5V.

Designed for use in battery-powered systems, the low

quiescent current, 12

µA operating and 6µA in

shutdown, makes them an ideal choice. The quiescent

current is well controlled; it does not rise in dropout as it

does with many other low dropout PNP regulators.

Other features of the LT1521/LT1521-3/LT1521-3.3/

LT1521-5 include the ability to operate with very small

output capacitors. They are stable with only 1.5

µF on the

output while most older devices require between 10

µF and

100

µF for stability. Small ceramic capacitors can be used,

enhancing manufacturability. Also, the input may be con-

nected to voltages lower than the output voltage, including

negative voltages, without reverse current flow from out-

put to input. This makes the LT1521 series ideal for backup

power situations where the output is held high and the

input is low or reversed. Under these conditions only 5

µA

will flow from the output pin to ground.

300mA Low Dropout

Regulators with Micropower

Quiescent Current and Shutdown

FEATURES

5V Battery-Powered Supply with Shutdown

Dropout Voltage

s

Dropout Voltage: 0.5V

s

Output Current: 300mA

s

Quiescent Current: 12

s

No Protection Diodes Needed

s

Adjustable Output from 3.8V to 20V

s

Fixed Output Voltages: 3V, 3.3V, 5V

s

Controlled Quiescent Current in Dropout

s

s

Reverse Battery Protection

s

No Reverse Current

s

Thermal Limiting

OUTPUT CURRENT (mA)

0

0

0.1

0.2

0.3

0.4

0.6

50

100

150

200

LT1521 • TA02

250

300

0.5

8

5

1

2

3

+

6V

1.5

µF

1

µF

5V

300mA

<0.25

OFF

>2.80

ON

NC

ON

LT1521-5

GND

IN

SHDN

OUT

SENSE

LT1521 • TA01

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

s

Low Current Regulator

s

Regulator for Battery-Powered Systems

s

Post Regulator for Switching Supplies