Heatsink for CC8X modules

Embedded Devices Linux
1

Hi

Is there a reference design for heatsink / thermal spread for CC8X modules ?

2

Digi engineering has done some research on this. For details contact Tech.Support@digi.com reference CC8X-206 and CC8X-280.

here are some summaries:

Conclusions

The heatsink undoubtedly improves the heat evacuation of the SOM. The biggest differences are observed with the climatic chamber switched-off, which means there’s not any forced convection on the system (the climatic chamber has a fan inside that helps cooling the device). In this scenario (which is closer to real life than with the climatic chamber ON) the temperature difference between using and not using the heatsink goes up to around 20ºC.

There are barely differences by using the two heatsink configurations: on top of the shield and on top of the SOM components. However, there is an additional improvement on the heat evacuation by adding thermal conductive adhesive transfer tape between the shield and the heatsink. This helps to keep a much more homogeneous temperature on the SOM, easing the transfer of the heat from the CPU to the heatsink. That will be the most efficient configuration.

In order to be able to properly assembly the heatsink in top of the shield using a conductive adhesive transfer tape, the spring height should be reduced or the screw height increased.

Software/firmware recommendations:

Recommendations

recommendations that could be studied and implemented from a software point of view to reduce the module temperature as much as possible:

  • WiFi contributes with around 2-3 ºC to heat up the system when it is enabled. The recommendation here is to turn off the WiFi radio when it is not being used.
  • recomentation here is to reduce the screen frequency to avoid the screen to heat up too much when it is not really necessary to run at high frequencies…
  • The GPU is one of the main heat contributors to the system when the device is graphical operation. The recommendations here are:
    • Reduce the number of visible graphics if possible
    • Reduce the drawing frequency if possible (increment the time between screen redraws)
    • Perform a dynamic GPU frequency management. By reducing the clock divisor from 64 to 16 you can cool the system around 7ºC.
  • The CPU frequency does not make a big difference but, since the performance does not seem to be affected, it is better to force a lower frequency to reduce consumption and temperature.
  • When the device is charging, the temperature raises around 7-8ºC. The recommendations here are:
    • Put the device in low power mode/suspend status when the device is charging
    • Turn off the screen when the device is charging
    • Perform dynamic CPU power management when the device is charging