Why must the VCCA be powered in Cyclone 10 LP even if PLLs are not being used?
At least one reason is that the internal power on reset circuit also monitors VCCA. So it won't come out of power on reset untill all supplies, including VCCA, are detected. The power on reset keeps monitoring VCCA for brownouts to reset it if VCCA sags. But it does not monitor VCCIO for brownouts.