Does PLL VCCA require isolation if PLL isn't used?

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Even if the PLL is not used, the VCCA power must be connected to a 1.5-V supply. The power connected to VCCA must be isolated from the power to the rest of the Cyclone FPGA.

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In my opinion, the second clause doesn't refer to the first. Standard VCCINT bypass should be sufficient in this case.

As an additional remark, if you intended to use the PLL though: VCCA isolation mainly means separate bypass caps and a filter (R or ferrite) to VCCINT. If you place the caps (I have typically 1n + 100n) directly between VCCA and GNDA, there's no particular purpose of 1. a separate plane, 2. a VCCA island, 3. thick traces.