Multiple power supplies are required to power a device and must be provided in a specific sequence. Consider the use of power monitoring or sequencing circuitry to provide the correct power-on sequence to the device as well as any additional active components on the board. More complex environments might benefit from the use of a microcontroller or system and power management bus such as SMBUS or PMBUS to control the power and reset process. Specific details regarding on/off sequencing can be found in the device data sheet. For more information on supply consolidation and topologies, see the 7 Series FPGAs PCB Design Guide (UG483), UltraScale Architecture PCB Design User Guide (UG583), or Zynq 7000 SoC PCB Design Guide (UG933) depending on your device.
The separate sources provide the required power for the different device resources. This allows different resources to work at different voltage levels for increased performance or signal strength, while preserving a high immunity to noise and parasitic effects.