SNOSBT0L February   2000  – September 2016 LM340

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     Available Packages
  3. 3 Description
    1.     Fixed Output Voltage Regulator
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 LM340A Electrical Characteristics, VO = 5 V, VI = 10 V
    6. 6.6 LM340 / LM7805 Electrical Characteristics, VO = 5 V, VI = 10 V
    7. 6.7 LM340 / LM7812 Electrical Characteristics, VO = 12 V, VI = 19 V
    8. 6.8 LM340 / LM7815 Electrical Characteristics, VO = 15 V, VI = 23 V
    9. 6.9 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Output Current
      2. 7.3.2 Current Limiting Feature
      3. 7.3.3 Thermal Shutdown
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Shorting the Regulator Input
      2. 8.1.2 Raising the Output Voltage Above the Input Voltage
      3. 8.1.3 Regulator Floating Ground
      4. 8.1.4 Transient Voltages
    2. 8.2 Typical Applications
      1. 8.2.1 Fixed Output Voltage Regulator
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
    3. 8.3 System Examples
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Heat Sinking DDPAK/TO-263 and SOT-223 Package Parts
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Related Links
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

10.3 Heat Sinking DDPAK/TO-263 and SOT-223 Package Parts

Both the DDPAK/TO-263 (KTT) and SOT-223 (DCY) packages use a copper plane on the PCB and the PCB itself as a heat sink. To optimize the heat sinking ability of the plane and PCB, solder the tab of the plane.

Figure 29 shows for the DDPAK/TO-263 the measured values of θ(J–A) for different copper area sizes using a typical PCB with 1-oz copper and no solder mask over the copper area used for heat sinking.

LM340 LM340A LM7805 LM7812 LM7815 00778139.pngFigure 29. θ(J–A) vs Copper (1 Ounce) Area for the DDPAK/TO-263 Package

As shown in Figure 29, increasing the copper area beyond 1 square inch produces very little improvement. It should also be observed that the minimum value of θ(J–A) for the DDPAK/TO-263 package mounted to a PCB is 32°C/W.

As a design aid, Figure 30 shows the maximum allowable power dissipation compared to ambient temperature for the DDPAK/TO-263 device (assuming θ(J–A) is 35°C/W and the maximum junction temperature is 125°C).

LM340 LM340A LM7805 LM7812 LM7815 00778140.pngFigure 30. Maximum Power Dissipation vs TAMB for the DDPAK/TO-263 Package

Figure 31 and Figure 32 show the information for the SOT-223 package. Figure 31 assumes a θ(J–A) of 74°C/W for 1-oz. copper and 51°C/W for 2-oz. copper and a maximum junction temperature of 125°C.

LM340 LM340A LM7805 LM7812 LM7815 00778141.pngFigure 31. θ(J–A) vs Copper (2 Ounce) Area
for the SOT-223 Package
LM340 LM340A LM7805 LM7812 LM7815 00778142.pngFigure 32. Maximum Power Dissipation vs
TAMB for the SOT-223 Package

See AN-1028 LMX2370 PLLatinum Dual Freq Synth for RF Pers Comm LMX2370 2.5GHz/1.2GHz (SNVA036) for power enhancement techniques to be used with the SOT-223 package.