Hi, for the Cyclone series FPGAs the PLL:s require 2.5V according to datasheets. And it says that this voltage shall be present even if they are not used.
In my application I don't use the PLLs and I have a 3.3V supply for I/Os which I have tried feeding also to the PLL supply pins. I do not really want to create a 2.5V supply only for functions that I don't use.
It seems to work for me, but do you anticipate any problems supplying 3.3V here? Since I do not use the PLL functions I don't care if they are out of spec, I just want everything else to work as intended.
By the way, I am using a semi-discrete PLL instead for less noise. See https://sm6vfz.wordpress.com/2020/08/21/pll-frequency-synthesis-with-programmeable-logic/ .
Which family device are you using? Please make sure that the applied voltage does not exceed the Absolute Maximum Rating specified in the datasheet. Check values of VCCA / VCCA_PLL / VCCD_PLL / VCCA_FPLL etc. related to your device.
Yes, it should be fine to use 3.3V as it is within Absolute Max and the feature is functionally unused.
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