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 ref-

erence, current limiting and thermal shutdown.

The LM1085 series is available in TO-220 and TO-263 pack-

ages. Refer to the LM1084 for the 5A 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

3A

n

Line Regulation

0.015% (typical)

n

Load Regulation

0.1% (typical)

Applications

n

High Efficiency Linear Regulators

n

Battery Charger

n

Post Regulation for Switching Supplies

n

Constant Current Regulator

n

Microprocessor Supply

Connection Diagrams

TO-220

10094702

Top View

TO-263

10094704

Top View

Basic Functional Diagram,

Adjustable Version

10094765

Application Circuit

10094752

1.2V to 15V Adjustable Regulator

June 2005

© 2005 National Semiconductor Corporation

DS100947

www.national.com