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ESDS304: Uses on 1000BASE-T interface

Part Number: ESDS304

Hi E2E Team,

I am planning to use ESDS304 in my design to protect the Ethernet interface (1000BASE-T) from ESD and EFT. As per my understanding the 1000BASE-T signals are encoded using PAM5 encoding scheme in which voltage levels can be between +1V to -1V. Please refer to below image-

When signal voltage level goes to negative, the ESD diode will be in forward bias.  As per datasheet Vf is 0.8V (typical). So when -1V will appear on the signal line the ESD diode will reduce the voltage to -0.8V from -1V.

My question here is what will be the impact of the above mentioned scenario in the normal operation of the interface? Would Ethernet interface work normally in long run on we can face issues due reduced voltage levels?

Best Regards,

Aditya Kumar Singh

  • Hi Aditya,

    Could you share what Ethernet PHY you are using for this application? For the lines going from the RJ-45 connector to the PHY, I haven't seen a signal that goes below ground like this. This encoding might be for the lines going from the PHY to the CPU, which seldom need ESD protection, since they are internal lines. 

    To answer your question, ESDS304 would impact the normal operation of this interface. While the typical forward voltage is 0.8 V, we cannot guarantee that it will not be lower. When using a unidirectional diode like this, it's best to keep the normal operating voltage levels on the line between 0 V and the Vrwm to ensure that your signal integrity isn't compromised. 


    Matt Smith