LimeSDR FPGA Power Supply

Dear Lime Team,

I have a question regarding the FPGA power supply. Looking at the power diagram it seems like the FPGA receives the 3.3V, 1.8V and 2.5V from the ADP2386 power regulator and subsequent power regulators. Is there a specific reason why the 1.2V power supply (yellow) is connected to the internal power bus and not to the 3.3V power regulator (red circles)? (see sketch)

It seems to be easier to connect the 1.2V power supply to the 3.3V power regulator and utilize a AP7361 instead of the ADP2384.

Thank you very much.

I am guessing it is because of the high current requirements of the 1.2V power supply for the FPGA. Or are there any other major reasons for this design?

Hi @Sombrero,

Both ADP2384 and ADP2386 are switching power regulators. Hence the efficiency of this approach is much better. Moreover, ADP2386 is quite loaded already and 1.2V rail is power hungry.

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Thank you very much, this answers my question. :slight_smile: