I’m working closely with a customer that has some doubts regarding how the temperature sensor works and what kind of temperature ranges the module can tolerate and how we can assure some maximum safe values.
I’ve been constantly checking the imx-thermal.c source code plus our developer site reference to Thermal Management, however, as the customer made some additional tests I would like to check with you.
I’ve already explained to the customer that we test normal behaviour under a 85ºC environment - temperature chamber (in Colibri iMX6ULL IT’s case), so that we can guarantee that under a 85ºC environment the module works without issue. I’ve also explained to them that even though the SoC can tolerate higher temperatures overall, the ideal maximum temperature is 85ºC. Anywhere higher than that can damage the module. Kindly confirm this or add more information that you see fit, as the customer is concerned that in a 85ºC environment the temperature of the module would likely raise in that case.
Regarding the tests, the customer placed a temperature sensor (Thermocoupler) on top of the SoC and made some tests:
In a 60ºC environment, they turned on the module (in the prototype casing) and the temperature measured by the thermocoupler was 75ºC while the value measured by the internal sensor (
cat /sys/devices/virtual/thermal/thermal_zone0/temp ), read 95ºC, making a 20ºC difference between exterior and interior of the CPU/SoC. This raised some questions:
Is this temperature difference correct/normal/intended/expected? What are our comments in this regard?
Acording to an additional temperature sensor in the casing, the temperature inside the case is about 65ºC while the SoC temperature sensor read 95ºC, a 30ºC difference. Our line of reasoning is that if, instead of 65ºC, the casing reads 85ºC as a constant value inside and what we assume to be the temperature module (and what we state as a maximum safe value), the value would quickly raise up to 115ºC (throttling/turning off depending on the values on the
Is there any way we guarantee a 85ºC as a maximum safe value, how we can measure that, and if there is any way on preventing to surpass that temperature apart from the SoC failsafe methods?
What does the 85ºC exactly mean and how it works as a guarantee for the customer that it is a safe temperature to work with (inside a casing, etc.) given that during operation temperature would likely increase if there is not enough cooling?
Thanks and regards,