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Altera_Forum's avatar
Altera_Forum
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9 years ago

Cyclone IV PLL min input frequency

Hi, What is minimum input clock for Cyclone IV E PLL? Data sheet states that minimum Fin=5MHz, but PLL locks even to 500KHz input clock freqency. Can someone explain this to me? Thanks
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

As you've found, the spec states fIN(min)=5MHz. Don't rely on all devices operating correctly if you're operating them out of spec.

The only suggestion I have is that the PLL is locking to some harmonic content of your clock source.

Cheers,

Alex