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Protecting Circuit - ESD

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Full Member level 6
May 10, 2020
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I'd like to know on how to select the transient protection circuit components for my Ethernet Interface.

I saw a reference design that uses a pair of UCLAMP3301D and 2.2Ω series resistors to the jack to protect that PHY against rapid disconnect/connect transients as shown below.

enter image description here

I'd like to know the purpose of 2.2ohm resistor and how to select a different value if the diodes are different?

Can someone tell me whether the specifications of UCLAMP3301D are correct? If not, what should be the right set of specifications for this component for transient protection? Just want to understand the logic so that I can search for cheaper alternative components (if any available)

The above image is for KSZ8863 device. I need to design a circuit for KSZ9131 device. Can you please help?

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.

Important spec for fast data lines, low capacitance according to the respective interface requirements. Current/power rating for the required ESD level, always specified in ESD diode datasheet. Voltage rating for data lines usually 3.3 or 5V.

I'd like to Microchip products, it is easy to run. Don't need care to much like other cheaper brand.
It mean that Microchip already know some issue with real condition when designer make a "mess" of components on PCB ;). So, they release this appnote: AN2587 - EMI, EMC, EFT, and ESD Circuit Design Consideration
The key point to protect ESD is creating a way for high voltage go through, and this way not through important parts or "weak" parts and make it spoil.
The key point for EFT is harder, it effected by design, layout, mechanic, and structure inside IC. Example, with same part BUCK converter, same footprint, same parameters, 01 part failed EFT and 01 part pass easily. The difference is the passed part have monitor switching current directly, the failed part using undirectly monitor switch current through voltage on switching point.
EMC, long story ...

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