Power sharing - FPGA & HPS power supply

[Altera_Forum]

Dear community, 

 As you know, the HPS unit and the FPGA unit of the Cyclone V SXF need different voltage supplies, for instance  1.1 V for the core 1.5 V for the DDR3 and corresponding banks on the FPGA and HPS 2.5 V or 3.3 V for GPIOs Now seeing that as for instance the HPS core and the FPGA core both need 1.1 V - I would just connect them to the same power supply. However, the Altera Cyclone V Development Board uses separate supplies for FPGA and HPS. In the "Cyclone® V Device Family Pin Connection Guidelines" (please google, I cannot post anything if I insert a link) both approaches are outlined. So my question is: What are the problems associated with connecting FPGA and HPS to the same power supply? If there aren't any, why does the Development Board have separate supplies?  Many thanks, Claudia

[Altera_Forum]

When share power supply, not only the FPGA and HPS, but also other chips whose work frequence is very high, will be effected by each other. When we design a high-speed PCB(such as dac or adc), we always separate power supplies for each chips. Maybe you can learn some knowledge about digital and analog circuit. Then you can understand it better.

[Altera_Forum]

The Mpression Helio Board uses the same power supply for the FPGA and the HPS. I never had the board in my fingers but it doesn't seem to be such a bad idea after all to share the power supplies! 

(See Mpression Helio Board Reference Manual on Page 41)

[Altera_Forum]

Sharing the power supplies maybe causes a problem occationally not always. Separating the supplies is better. By the way, you can see a lot of capacitance on the back of the development board.You can pick some off and the development board can work normally as well. This design helps to make the development more robust. Without them it maybe work normally as well but you'd be better to add them to the developmont board or other digital circuit.

[Altera_Forum]

The leaders in electronic components must use only one power to own device! 

Anyway on outside need will stand power converters, internal circuit will decrease the footprint. And then ordering of power supply may be maked internally, without external controller.