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Choose connector and Ethernet Transceiver for MCU ethernet interface.

Associate III

Hi, I need to add an ethernet interface to a STM32H745IIT6 MCU. I have to choose the RJ45 connector and the Ethernet Transceiver chip.

I state that I've never done this thing, so my idea was to take the Nucleo board schematic and use the same connector and the same chip. The problem is that both the connector and the chip are not available now (unless exorbitant costs), so I would like to select another connector and another chip, but I practically don't know where to start. I don't know what parameters to see and how to choose these components. I need some help.

For the connector, I saw that the Wurth catalog is well stocked, and there are also connectors with integrated magnets that would help reduce the BOM. But I don't know which to choose among all these connectors:

For the Ethernet Transceiver chip, I saw that they use an LAN8742A-CZ-TR on the nucleo board, and I should select an alternative to this chip. Searching the internet there are thousands of alternatives, but I don't know how to figure out which one is suitable for my application (use with an STM32H745IIT6).

Can anyone help me select some parts or can you tell me about the chip + connector already used in other similar applications, and which have no problems.

Thanks in advance

ST Employee

 hi federico

for the RJ45 in wruth , you can use 10/100BASE-T series, for which to use is based on your application. 

for LAN8742A-CZ-TR, the LAN8742AI-CZ-TR is also can be used in the system. 

ST Employee

To select Eth PHY, normally you need to consider the interface MII or RMII between MAC/MCU and PHY, and if external clock or internal oscillator in the PHY is preferred. And the cost and lead-time of this PHY could be considered also.


About RJ45 connector, transformer embedded in the connector is OK also if the size of this connector is acceptable. and you may need to pay attention on the Turn Ratio of transformer must be 1CT:1CT.