LM1085

3A Low Dropout Positive Regulators

General Description

The LM1085 is a series of low dropout positive voltage regulators with a maximum dropout of 1.5V at 3A of load current. It has the same pin-out as National Semiconductor’s industry standard LM317.

The LM1085 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 integrate the adjust resistors.

The LM1085 circuit includes a zener trimmed bandgap reference, current limiting and thermal shutdown.

The LM1085 series is available in TO-220 and TO-263 packages. Refer to the LM1084 for the 5A version, and the LM1086 for the 1.5A version.

Features

• Available in 3.3V, 5.0V, 12V and Adjustable Versions
• Current Limiting and Thermal Protection
• Output Current                         3A
• Line Regulation    0.015% (typical)
• Load Regulation       0.1% (typical)

Applications

• High Efficiency Linear Regulators
• Battery Charger
• Post Regulation for Switching Supplies
• Constant Current Regulator
• Microprocessor Supply

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

Maximum Input to Output Voltage Differential

    LM1085-ADJ                                                                      29V

    LM1085-12                                                                        18V

    LM1085-3.3                                                                       27V

    LM1085-5.0                                                                       25V

Power Dissipation (Note 2)                                Internally Limited

Junction Temperature (TJ)(Note 3)                                    150˚C

Storage Temperature Range                                -65˚C to 150˚C

Lead Temperature                                              260˚C, to 10 sec

ESD Tolerance (Note 4)                                                     2000V

Operating Ratings (Note 1)

Junction Temperature Range (TJ) (Note 3)

    Control Section                                                 −40˚C to 125˚C

    Output Section                                                  −40˚C to 150˚C

Connection Diagrams

Basic Functional Diagram, Adjustable Version

Simplified Schematic