4.2.6. Programmable Phase Shift
The programmable phase shift feature allows both fPLLs and I/O PLLs to generate output clocks with a fixed phase offset.
The VCO frequency of the PLL determines the precision of the phase shift. The minimum phase shift increment is 1/8 (for I/O PLL) or 1/4 (for fPLL) of the VCO period. For example, if an I/O PLL operates with a VCO frequency of 1000 MHz, phase shift steps of 125 ps are possible.
The Intel® Quartus® Prime software automatically adjusts the VCO frequency according to the user-specified phase shift values entered into the IP core.