The thermal design guide describes that the thermal resistance Theta JC of Orin NX 16G is 0.131℃/W, the reference power dissipation is 25W, and the temperature difference is about 3.275 °C, but the measured temperature difference can reach more than 8 °C。
Is the thermal resistance Theta JC provided in the thermal design guide accurate?
Hi, how did you get the 8°C difference? Please also note the temperature sensor accuracy is ± 3°C.
Thank you for your reply!
Currently I use thermocouples on the interface between the Orin NX CPU-Surface and the bottom-surface of our heatsink for temperature monitoring, the temperature at the top-side of the heatsink is about 70°C, Orin NX Tj can reach 91°C, the temperature of interface between the heatsink and Orin NX CPU is about 72-75°C, the main temperature band difference comes from Orin NX TJ and Orin NX Tc, it’s significantly more than 3.275℃。
Ps：The TIM for the interface between the Orin NX CPU-Surface and the bottom-surface of our heatsink，I tried using thermal grease and phase change materials, and the results were similar, both with relatively small nominal thermal resistance。
thermal grease：0.6 ℃ in^2/W
so, i think ,the real thermal resisitance Theta Jc is more than 0.131℃/W。
I don’t think your test is correct. If you want to observe the Tjc of Orin, you should remove heatsink, measure the temperature of Orin chip surface, read the internal sensor value of Orin chip, and then compare them. That’s the Tjc of Orin chip.
I also tested the situation you said，but there is a problem with this test:
Without a heatsink, the Orin NX cannot maximize the load (25W),because CPU TJ will soon exceed 105°C ，so i tested with only about 7W，and read Tj and Tc synchronously。
In the figure, we can see that Tj is 92.7°C and Tc is only 78.5°C。
I know that there are some inaccuracies in the current environment, but the thermal resistance of 0.131°C/W does not seem to be quite aligned.
At present, the design of our heat sink is nearing completion, but the thermal resistance parameters are not yet completely certain. I just want to know more about this thermal resistance parameter for future thermal solution design.
0.131°C/W is the Tjc only for 19.8W as you can see in TDG.
Okay！Thank you for your reply!
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