# thermal solution calculation for TX1

Hi
I am using Jetson TX1 som in a system i have considered that junction temperature allowed is <90 and maximum ambient temperature is <65 If I need to meet this two condition the heat sink resistance value i am getting is very low θPA-HS is heat sink resistance value selected to keep tegra below 90 degree TPexp is the expected plate temperature and TJ is the expected junction temperature with the selected heat sink resistance

θjp TA TP PdMax θPA θjA θPA-HS TPexp TJexp

1 65 74 15 0.6 1.6 0.1 66.5 81.5
0.6 65 80 15 1 1.6 0.1 66.5 75.5
1.6 65 65 15 0 1.6 0.1 66.5 90.5

I have calculated the thermal resistance of heat sink it is coming with a very low value practical heat sink will have value more than this how to select the thermal resistance of the heat sink in this case

If We choose heat sink with low thermal resistance it is increase the plate temperature maintaining the junction value below the expected level

Book1.xls (23.5 KB)

The maximum TTP operating temperature could be 80, why do you set TPexp as 66.5? TPexp is so close to TA, that cause the θPA is too low. Are you using the original TX1 module?

Per design guide, in most use case, θjp = 1.0 or 0.6, your θja = 1.67, so the θPA could be 0.67 or 1, if TPexp < 80.

http://developer.nvidia.com/embedded/dlc/jetson-tx1-thermal-design-guide

Dear sir

Thanks for the information we are using jetson tegra TX1 SOM ,Texp is not the fixed value,to keep the junction below 89 and the plate below 80 it is the calculated expected value for the selected heatsink thermal resistance .we got the value of θPA as very small value to keep the TJ less than 89

considering the overall thermal resistance as the sum off resistance of the heat sink i have selected and the resistance of the plate in three scenarios When I calculate the junction temperature with this overall thermal resistance it is very high i.e it is greater that 89 refer last column

θJP TJ TA TP P θPA θJA θPAS TPe TJe

1 89 65 74 15 0.6 1.6 1 80 95
0.6 89 65 80 15 1 1.6 1 80 89
1.6 89 65 65 15 0 1.6 1 80 104

FORMULAS USED

TP=TJ-θjp*P

θPA=(TP-TA)/P

θJA =θJP+θPA

θPAS----for SELECTED heat sink
TPe expected with the selected heat sink
TPe=P*θPAS+TA
TJe=(θPAS+θJP)*P+TA

Kindly let me know were i went wrong ,IS the method of calculating the expected junction temperature when adding a heat sink i followed is correct
in this i am getting 104 degree when my resistance(thermal resistance ) is more the heat generated at the core is accumulated and temperature is increased please correct if i am wrong

Your calculation is correct. θPAS+θJP = (TJe-TA) / P, If P=15w, TA=65, TJ <90, θPAS+θJP should be < 1.67. As θJP could be 0.6/1.0/1.6 per use case, θPAS will be 1.01/0.67/0.01