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August 2002
LM1084
5A Low Dropout Positive Regulators
General Description
The LM1084 is a series of low dropout voltage positive
regulators with a maximum dropout of 1.5V at 5A of load
current. It has the same pin-out as National Semiconductor’s
industry standard LM317.
The LM1084 is available in an adjustable version, which can
set the output voltage with only two external resistors. It is
also available in three fixed voltages: 3.3V, 5.0V and 12.0V.
The fixed versions intergrate the adjust resistors.
The LM1084 circuit includes a zener trimmed bandgap ref-
erence, current limiting and thermal shutdown.
The LM1084 series is available in TO-220 and TO-263 pack-
ages. Refer to the LM1085 for the 3A version, and the
LM1086 for the 1.5A version.
Features
n Available in 3.3V, 5.0V, 12V and Adjustable Versions
n Current Limiting and Thermal Protection
n Output Current
5A
n Industrial Temperature Range
−40˚C to 125˚C
n Line Regulation
0.015% (typical)
n Load Regulation
0.1% (typical)
Applications
n Post Regulator for Switching DC/DC Conveter
n High Efficiency Linear Regulators
n Battery Charger
Connection Diagrams
TO-220
Application Circuit
Top View
10094636
TO-263
10094635
Top View
Basic Functional Diagram, Adjustable Version
10094652
1.2V to 15V Adjustable Regulator
10094665
© 2002 National Semiconductor Corporation DS100946
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Typical Performance Characteristics
Dropout Voltage (VIN−VOUT)
Short-Circuit Current
Load Regulation
10094663
10094671
LM1084-ADJ Ripple Rejection
10094638
LM1084-ADJ Ripple Rejection vs Current
Temperature Stability
10094643
10094690
5
10094625
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Typical Applications (Continued)
10094659
Battery Backup Regulated Supply
Automatic Light control
10094661
Generating Negative Supply voltage
10094662
Ripple Rejection Enhancement
10094660
Remote Sensing
10094658
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