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Power Over Ethernet Interoperability Guide by Sanjaya Maniktala

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Should D1 Be a TVS?
Historically, some OEMs went a step further and started suggesting that this low-cost standard slow-port diode (typically 1A/100 V) be replaced by a transient-voltage suppressor (TVS) diode (a TVS is just a rugged zener diode). Note that this new suggested port TVS diode is in addition to the single TVS routinely placed at the input side of the PSE board, that is, between the “48V” power supply and the PSE chips (the usual SMAJ58A). The thought is that using a TVS will somehow provide some protection from an undefined “spike” that may appear on the output (cable side).
This new port TVS will certainly add to the cost since it is 3 to 5 cents per port. It is yet to be seen what real advantage it offers, and under what specific ...

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