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Altera_Forum
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9 years ago

CycloneIV VCCD_PLL Decoupling

Hi, what is the appropriate ground connection for the VCCD_PLL pins? None of these have GND pins nearby in the E22 package, but the name suggests that this is a digital pin, so it is refer...
Altera_Forum's avatar
Altera_Forum
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9 years ago

Yes, vias next to the caps are the next step here, because I still need to actually connect all these pins to the supply rails.

For the connection between the caps and the pins, the only thing that could possibly have a lower inductance than a 2mm x 0.2mm trace would be a via to a cap on the bottom, but that is probably the same order of magnitude as the inductance of the bond wires inside the IC.

Placing the caps on the bottom would indeed give a shorter path to whatever GND is the return path for the VCCD_PLL supply pin, but even then it would be good to know which one it is. I'd like to avoid parts on the bottom though.