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Altera_Forum
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13 years ago

Cyclone III PLL loses lock at >75C

I am using PLL reconfiguration. When the FPGA is powered up the PLL is loaded with different M, N and C values for the frequency I want to generate. The PLL will lock below 75C but once it gets t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

How are you measuring the 75C? and how are you getting your part up to that temp?

Do you have a thermal couple right on the case of the part, or are you using the chamber temperature?

The ambient temp near the part may easily be greater that 10C above chamber temperature, especially if the part is in a box under a heat shield with zero air flow.

The junction temperature is what really matters, but that's hard to directly measure, so getting a case temp is your best bet. If you device is under a heat shield, with zero air flow the temp of the part may be significantly hotter than you expect based on your chamber temp.

Pete