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Sangesh , 05-29-2024, 10:20 AM

Hi team, am looking for explanation on Phy IC and significance of PHY IC and why do we need to use it for USB, Ethernet & PCIe. Why we are not concerned with I2C, SPI for Phy IC? For which protocols we need to concern on Phy IC?

QDrives , 05-29-2024, 03:16 PM

The simplest answer is that USB and ethernet go off board with long(er) cables.
If there is high voltage (ESD, EFT or surge) on them, you do not want that voltage in you main controller.
I2C and SPI are to be used on the same board. Whenever you go of the board, it is advised to add protection, filtering, repeaters, etc. to protected the internal side from the outside world.

Robert Feranec , 05-30-2024, 06:14 AM

I would also add, PHY is usually changing standard digital signals and levels to the interface specific signals and voltage/current levels. So, very simply to say, you often need PHY for interfaces and peripherals which are not 3V3 signals.