Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
19 years ago

VCCA_PLLn

I know the Stratix II device handbook says I must connect the VCCA_PLLn even if I'm not using PLLn. But do I really have to? What will happen if I don't? I want to save all the power I can.
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
19 years ago

I think the internal VCCAs are connected together for all PLLs inside the device, so if you couple noise onto the VCCA of a PLL you are not using (by not filtering its VCC), it could affect the PLLs you are actually using. Now whether this happens in practice is another story. It will depend on your specific system and frequencies & PDN involved I would think.