Case temp vs. junction temp

[Altera_Forum]

Hello, 

 I have a board with an Arria GX on it with no heat sink. The case temperature of the FPGA stabilizes around 55 degree C. I am trying to figure out how that translates to the junction temp Tj (which is 0 to 85 per the data sheet.) The data sheet also gives the junction to case thermal resistance θJC = 0.3 degree C / W.  Does this mean that Tj = 55 + θJC * P  where P is the power dissipated by the device. This device should be drawing less than 5W. This would translate to a Tj of 56.5 degree C.  Does this sound correct?  Thank you for your help!

[Altera_Forum]

Yes that looks correct. 

The power analyser in Quartus should also be able to give you an approximation of the junction temperature. IIRC you can tell it that you don't have any heatsink on the chip.

[Altera_Forum]

Thanks Daixiwen! I did use PowerPlay early on as an estimate but I do not have an accurate test vector file to get a more accurate result. So far the measurements seem to be below the worst case scenarios I plugged in during the design phase. 

 Thank you!