I'd like to understand how to select a clamping protection device, say TVS/ESD diodes, for Ethernet/USB lines ?

Like, what should be the current rating and the clamping voltage rating for the ESD diode to be placed on the datalines?

What is the thumb rule of the spec? Just trying to learn the good practices.

  • \$\begingroup\$ What are you trying to protect (i.e. the potential victim) and from what (the aggressor)? <-- you begin here. \$\endgroup\$
    – Andy aka
    Commented Oct 25, 2022 at 9:42
  • \$\begingroup\$ Could you please explain a little bit more @Andyaka? Like can you provide an answer with a sample example? For example, in Ethernet devices, I am trying to protect the PHY device. \$\endgroup\$
    – user220456
    Commented Oct 25, 2022 at 18:20
  • \$\begingroup\$ What specific part of its maximum ratings are you trying to stop being exceeded @newbie? \$\endgroup\$
    – Andy aka
    Commented Oct 25, 2022 at 18:30

1 Answer 1


They are application specific so it really depends what is it that you are protecting and from what you are protecting it. Obviously a consumer device you use indoors requires less protection than some equipment outdoors that must survive lightning strikes.

Even in your case, the "Ethernet" or "USB" really means nothing, as there are so many types of Ethernet (speeds, PoE or not) and USB. Each of them requires different kind of protection because they are different and have different requirements for protection.

There might be standards how much protection is needed, and you may want more protection in harsh environment.

Voltage must be high enough and capacitance must be low enough so protection does not interfere much with normal operation.

Voltage must also be low enough that the protected item can handle it.

Current depends on how much protection you need.

Selection of protection device depends also on how fast, or how long the surges are.

It also depends how much protection the protected item has built into it.

So rule of thumb is, read application notes about it, preferably ones that match your chip or interface type. Protection devices usually have a list of what they are suitable for.

  • \$\begingroup\$ Thank you for your answer! Could you just add an example (considering any standard, say for Ethernet PoE or Standard) , mentioning what device to select and how the voltage spec should be considered? \$\endgroup\$
    – user220456
    Commented Oct 25, 2022 at 7:34
  • \$\begingroup\$ I'd like to build a protection for 1G Ethernet. Could you please provide an example for that in your answer? Its for industrial \$\endgroup\$
    – user220456
    Commented Oct 25, 2022 at 7:35

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