LT1129/LT1129-3.3/LT1129-5
Micropower Low Dropout
Regulators with Shutdown
FEATURES
DESCRIPTION
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The LT ®1129/LT1129-3.3/LT1129-5 are micropower low
dropout regulators with shutdown. The devices are capable
of supplying 700mA of output current with a dropout
voltage of 400mV at maximum output. Designed for use
in battery-powered systems, the low quiescent current,
50μA operating and 16μA in shutdown, make them an ideal
choice. The quiescent current does not rise in dropout as
it does with many other low dropout PNP regulators.
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400mV Dropout Voltage
700mA Output Current
50μA Quiescent Current
No Protection Diodes Needed
Adjustable Output from 3.8V to 30V
3.3V and 5V Fixed Output Voltages
Controlled Quiescent Current in Dropout
Shutdown
16μA Quiescent Current in Shutdown
Stable with 3.3μF Output Capacitor
Reverse Battery Protection
No Reverse Output Current
Thermal Limiting
Surface Mount SOT-223 and DD-Pak Packages
APPLICATIONS
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Low Current Regulator
Regulator for Battery-Powered Systems
Post Regulator for Switching Supplies
5V to 3.3V Logic Regulator
Other features of the LT1129 /LT1129-3.3/LT1129-5 include
the ability to operate with small output capacitors. They
are stable with only 3.3μF on the output while most older
devices require between 10μF and 100μF for stability. Also
the input may be connected to ground or a reverse voltage
without reverse current flow from output to input. This
makes the LT1129/LT1129-3.3/LT1129-5 ideal for backup
power situations where the output is held high and the
input is at ground or reversed. Under these conditions,
only 16μA will flow from the output pin to ground. The
devices are available in 5-lead TO-220, 5-lead DD-Pak and
3-lead SOT-223 packages.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
5V Supply with Shutdown
Dropout Voltage
0.6
IN
OUT
1
+
LT1129-5
VIN > 5.5V
4
SENSE
5V OUT
500mA
2
3.3μF
SOLID TANTALUM
SHDN
GND
3
VSHDN (PIN 4) OUTPUT
OFF
< 0.25
ON
> 2.8
ON
NC
0.5
DROPOUT VOLTAGE (V)
5
0.4
0.3
0.2
0.1
112935 TA01
0
0
0.1
0.5
0.2 0.3 0.4
OUTPUT CURRENT (A)
0.6
0.7
112935 TA02
112935ff
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