Doh! My PLLs lose lock. Crosstalk?

Hi there.

Yes, that is possible. It's a custom board and I did not provide special filtering to the PLL power pins unfortunately. However I measured it and the local 3v3 power plane seems quite clean.

I begin to think the problem is deeper than the PLLs, because I still get data problems even when I don't use the PLL. I suspect some sort of data crosstalk inside the device. This seems a weird idea (after all my years designing with CPLDs) so I am open to any suggestions :)

Pete

--- Quote Start ---

Hi snaarman,

do you use a custom board or an Altera Development Kit??

I ask you this because I had similar problem with the PLL in mine custom board and the problem was in the power supply.

At the beginning of the project I used only one PLL and all worked fine, I discovered the problem when I added a second PLL.

When the second one locked the clocks signal the first one lost the lock signal.

I solve the problem modifying the clock frequencies of the second PLL to fit in the first one because, in my case, to change the power supply became too much expensive.

I hope that this post can help you.

--- Quote End ---