LT1521/LT1521-3
LT1521-3.3/LT1521-5
300mA Low Dropout
Regulators with Micropower
Quiescent Current and Shutdown
FEATURES
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DESCRIPTION
The LT
®
1521/LT1521-3/LT1521-3.3/LT1521-5 are low
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, 12µA 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 1.5µF on the
output while most older devices require between 10µF and
100µF 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 5µA
will flow from the output pin to ground.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Dropout Voltage: 0.5V
Output Current: 300mA
Quiescent Current: 12
µ
A
No Protection Diodes Needed
Adjustable Output from 3.8V to 20V
Fixed Output Voltages: 3V, 3.3V, 5V
Controlled Quiescent Current in Dropout
Shutdown I
Q
= 6µA
Reverse Battery Protection
No Reverse Current
Thermal Limiting
APPLICATIONS
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Low Current Regulator
Regulator for Battery-Powered Systems
Post Regulator for Switching Supplies
TYPICAL APPLICATION
5V Battery-Powered Supply with Shutdown
8
IN
LT1521-5
5
SHDN
GND
3
SENSE
2
OUT
1
5V
300mA
0.6
0.5
DROPOUT VOLTAGE (V)
+
6V
1µF
1.5µF
0.4
0.3
0.2
0.1
V
SHDN
(PIN 5) OUTPUT
<0.25
OFF
>2.80
ON
NC
ON
LT1521 • TA01
0
0
50
U
U
U
Dropout Voltage
100
150
200
250
OUTPUT CURRENT (mA)
300
LT1521 • TA02
1
LINER [ LINEAR TECHNOLOGY ]
