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LM340, LM340A, LM7805, LM7812, LM7815

SNOSBT0K – FEBRUARY 2000 – REVISED JULY 2016

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Product Folder Links: LM340 LM340A LM7805 LM7812 LM7815

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Copyright © 2000–2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LM340 and LM78xx are a family of fixed output positive voltage regulators with outputs ranging from 3 V to

15 V. They accept up to 35 V of input voltage and with proper heat dissipation can provide over 1.5 A of current.

With a combination of current limiting, thermal shutdown, and safe area protection, these regulators eliminate

any concern of damage. These features paired with excellent line and load regulation make the LM340 and

LM78xx versatile solutions to a wide range of power management designs. Although the LM340N and LM78xx

were designed primarily as fixed-voltage regulators, these devices can be used with external component for

adjustable voltage and current.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Output Current

With proper considerations, the LM340 and LM78xx can exceed 1.5-A output current. Depending on the desired

package option, the effective junction-to-ambient thermal resistance can be reduced through heat sinking,

allowing more power to be dissipated in the device.

7.3.2 Current Limiting Feature

In the event of a short circuit at the output of the regulator, each device has an internal current limit to protect it

from damage. The typical current limits for the LM340 and LM78xx is 2.4 A.

7.3.3 Thermal Shutdown

Each package type employs internal current limiting and thermal shutdown to provide safe operation area

protection. If the junction temperature is allowed to rise to 150°C, the device will go into thermal shutdown.

7.4 Device Functional Modes

There are no functional modes for this device.