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Altera_Forum
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16 years ago

Seperate PLL power planes for Cyclone III devices?

I have a question about PLL power supply. In "Cyclone III Device Family Pin Connection Guidelines", Altera requires a totally seperated VCCA & VCCD power island for Cyclone III PLLs. But...
Altera_Forum's avatar
Altera_Forum
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16 years ago

This question has been addressed elsewhere in the forum so you might try a search. The decision of whether or not you need to decouple the VCCA and VCCD pins from the other power supplies really depends on your design. Which device are you using? How many PLLs are you going to use? What frequencies are you going to run at?

Most likely you can get away without the separate power islands. At the very least you could probably just filter the main supplies to provide VCCA and VCCD. But again this depends on your design.

FvM might have a more in-depth response on this one.

Jake