LT1121/LT1121-3.3/LT1121-5
Micropower Low Dropout
Regulators with Shutdown
FEATURES
DESCRIPTION
The LT®1121/LT1121-3.3/LT1121-5 are micropower low
dropout regulators with shutdown. These devices are ca-
pableofsupplying150mAofoutputcurrentwithadropout
voltage of 0.4V. Designed for use in battery-powered sys-
tems, thelowquiescentcurrent, 30µAoperatingand16µA
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.
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0.4V Dropout Voltage
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150mA Output Current
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30µA Quiescent Current
No Protection Diodes Needed
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Adjustable Output from 3.75V to 30V
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3.3V and 5V Fixed Output Voltages
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Controlled Quiescent Current in Dropout
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Shutdown
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16µA Quiescent Current in Shutdown
OtherfeaturesoftheLT1121/LT1121-3.3/LT1121-5include
the ability to operate with very small output capacitors.
They are stable with only 0.33µF on the output while most
older devices require between 1µF and 100µF for stability.
Small ceramic capacitors can be used, enhancing manu-
facturability. Also the input may be connected to ground
or a reverse voltage without reverse current flow from
output to input. This makes the LT1121 series ideal for
backuppowersituationswheretheoutputisheldhighand
the input is at ground or reversed. Under these conditions
only 16µA will flow from the output pin to ground.
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Stable with 0.33µF Output Capacitor
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Reverse Battery Protection
ꢀ
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No Reverse Current with Input Low
Thermal Limiting
Available in the 8-Lead SO, 8-Lead PDIP, 3-Lead
SOT-23 and 3-Lead TO-92 Packages
APPLICATIONS
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Low Current Regulator
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Regulator for Battery-Powered Systems
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
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Post Regulator for Switching Supplies
TYPICAL APPLICATION
5V Battery-Powered Supply with Shutdown
Dropout Voltage
0.5
8
1
3.3V
OUT
IN
OUT
LT1121-3.3
150mA
0.4
0.3
0.2
0.1
0
+
1μF
5V
SOLID TANTALUM
5
SHDN
GND
3
V
(PIN 5) OUTPUT
SHDN
<0.25
>2.8
NC
OFF
ON
ON
LT1121 • TA01
80
OUTPUT CURRENT (mA)
0
20 40 60
100 120 140 160
LT1121 • TA02
1121fg
1