SPRADB7 September   2023 AM2431 , AM2432 , AM2434 , AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1 , AM263P4 , AM263P4-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

5.4.3 Calculated Thermal Resistance Values

Since the Control Card allows for the operating power to be recorded during the ambient temperature sweep, the thermal resistance between junction temperature and ambient temperature or RΘJA can be calculated using the following equation:

Equation 2. T J u n c t i o n - T A m b i e n t O p e r a t i n g   P o w e r   ( W a t t s ) = R Θ J A ( ⁰ C / W )

Table 5-3 shows the values for the max and average calculated values of RΘJA. The AM263x Sitara™ Microcontrollers Data Sheet includes a table that describes the Package Thermal Characteristics. An excerpt of the Package Thermal Characteristics table is shown in Table 5-4. Within this table, the values for thermal resistance based on a JEDEC defined 2S2P system can be found where the system is in the worst case device power consumption. The worst case values for RΘJA are 12.9, 11.8 and 11.1 ℃/W for 1, 2, and 3 meters per second air flow, respectively. For the non-simulated real world experiment, the calculated max values for RΘJA based upon measurements taken during the ambient temperature sweep are in line with the worst case device power consumption values from the data sheet. While the max values of RΘJA are near the worst case spec from the data sheet, the average value for RΘJA is considerably lower.

Note: Each measurement configuration was only run once and variance for each module measurement can result in calculated values of RΘJA having variance as well.
Table 5-3 Thermal Resistance Calculations
Measurement RΘJA Max (℃/W) RΘJA Average (℃/W)
CC only logging script with no Kapton tape on SoC 11.32 7.33
CC only logging script 11.88 8.16
CC logging script + Load Core 1 11.14 7.91
CC logging script + Load Cores 1,2,3 11.19 7.95
Table 5-4 AM263x Data Sheet Package Thermal Characteristics
Parameter Thermal Resistance Description ℃/W AIR FLOW (m/s)
RΘJC Junction to case 5.6 N/A
RΘJB Junction to board 5.7 N/A
RΘJA Junction to free air 18.6 0
RΘJA Junction to moving air 12.9 1
11.8 2
11.1 3