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Altera_Forum
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12 years ago

PLL lock problem

Hi all, I have problems with the PLLs in a 5CGXFC7D6F31C6N. They don't lock. I can reduce my design to 4 PLLs as shown here: https://www.alteraforum.com/forum/attachment.php?attachmentid=8...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

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Hi,

One ALTPLL has about 5 outputs, since you are using the same reference frequency to generate the out freq., why don't use a single ALTPLL? instead of 4 PLLs.

Regards,

Uday

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Actually, one of the Cyclone 5 PLLs has up to 9 outputs. But the generated frequencies are restricted to a common divider. If you need frequencies which don't match this criteria you need different PLLs.

However, I solved my problem above, I forgott to connect a resistor to the RREF pin which then led to this very strange behaviour.

Oliver