We are using an Ultrascale KU025 device in our design. We have two HR banks powered at 2.5V and 4 HP banks powered at 1.8V.
After VCCINT/VCCINT_IO and VCCAUX/VCCAUX_IO have been powered on, should the 2.5V VCCO be powered on after the 1.8V VCCO supply? Or can both VCCO supplies be powered on at approximately the same time? Would it be a problem if the 2.5V comes up slightly before the 1.8V supply?
There is the recommended (int, aux, io), but other than that, any/all at once is permitted (no restrictions). Note Vccintio MUST be connected to Vccint, Vccauxio MUST be connected to Vccaux. Other than that, there is no restriction on sequence.
The specified starting currents only apply for the recommended sequence. For other sequences, the current may differ.
In 28nm (7 series), Vccint, Vccaux MUST precede Vcco for HR banks (the only MUST rule).