SPRADB7 September   2023 AM2431 , AM2432 , AM2434 , AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1 , AM2732 , AM2732-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 How to Use This Application Note
    2. 1.2 Glossary
  5. 2Thermal Resistance Overview
    1. 2.1 Junction Vs. Ambient Temperature
    2. 2.2 Package Defined Thermal Resistance Characteristics
    3. 2.3 Board Defined Thermal Resistances
  6. 3Board Design Choices that Affect Thermal Performance
    1. 3.1 Thermal Vias
    2. 3.2 Board Size
    3. 3.3 Air Flow, Heat Sinking, and Enclosures
    4. 3.4 Copper Thickness
    5. 3.5 Relative Position of Heat Emitters
    6. 3.6 Layer Count
    7. 3.7 Breaks in Thermal Pathing
  7. 4Thermal Design Best Practices Review
  8. 5AM263x EVM Thermal Comparison with Data
    1. 5.1 Test Setup and Materials
    2. 5.2 Measurement Logging Software
    3. 5.3 AM263x EVM Comparison
    4. 5.4 Measurement Results
      1. 5.4.1 Lid Temperature Readings
      2. 5.4.2 Power Readings over Temperature
      3. 5.4.3 Calculated Thermal Resistance Values
      4. 5.4.4 Recorded Junction and Ambient Temperatures
      5. 5.4.5 Calculated Junction Temperature at Ambient Temperature Extremes
  9. 6Using the Thermal Model
  10. 7References

3.3 Air Flow, Heat Sinking, and Enclosures

There are a few external influences that affect the thermal resistance between the junction and ambient temperature. If the system is going to be designed within an enclosure, a new additional thermal resistance must be accounted for. Now, what was previously the thermal resistance between junction and ambient air, is only the thermal resistance between the junction temperature and the air within the enclosure. Any changes in ambient temperature will have a greater impact on the junction temperature. It is important to offset the additional thermal resistance that an enclosure provides by improving the thermal resistance of other areas of the system.

One way to improve the thermal performance of a system within an enclosure is to introduce air flow. By including a fan on a cutout of the enclosure, the thermal resistance that is created by the enclosure is minimized. Additionally, air flow in general will decrease the thermal resistance of external surface area such as the package lid or the PCB itself.

Attaching a heat sink is a general solution to address thermal issues. However, it should be noted that using a heat sink only decreases the thermal resistance between junction and case temperature. A PCB with significant thermal dissipation flaws will not be fixed simply by adding a heat sink.

For best thermal performance:

  • Use an enclosure that is optimized for thermal performance
  • Include fans in the enclosure design
  • Use a heat sink attached to the BGA Case lid
  • Maintain consistent air flow to the system
Table 3-4 AM263x EVM External Cooling Comparison
Measurement TMDSCNCD263 LP-AM263
Air Flow N/A N/A
Heat Sink N/A N/A
Enclosure N/A N/A