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Gigabit Ethernet Magnetics

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kindaichinisan

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Who has used HX5401NL from Pulse before? If so, can show schematic?

How to decide what is the power rating of resistor? For example, in the GbE magnetics connection, I need 4x 75ohm resistors. How to know the power rating needed?

I also need 4x 10nF capacitor, how to know the voltage rating?
 

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It's just a regular gigabit ethernet transformer, like others.

You can refer to LAN controller application notes or data sheets of integrated magnetics RJ45 jacks about the specification of this parts. Ground decoupling capacitors are usually rated for 2 kV DC. 75 ohm resistors are for common mode wave suppression and don't need a particular power rating. The rating may matter however, if the port is connected erroneously to a PoE hub.
 

kindaichinisan

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It's just a regular gigabit ethernet transformer, like others.

You can refer to LAN controller application notes or data sheets of integrated magnetics RJ45 jacks about the specification of this parts. Ground decoupling capacitors are usually rated for 2 kV DC. 75 ohm resistors are for common mode wave suppression and don't need a particular power rating. The rating may matter however, if the port is connected erroneously to a PoE hub.

It seems like there are a lot of different schematics of ethernet transformer. Also different types of magnetics like 8-core and 12-core. Hence the connection may not be that simple.

I need the power rating of resistor because I am building a board and needs to choose what power rating to use, whether 0.1W, 1W, etc. I can choose the higher power rating but that will result in larger resistor size. Hence, I need to know how to calculate the power rating needed so as not to use very large resistor. Same reason applies for capacitor where I am looking at voltage rating.
 

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Differences are related are mainly related to common mode choke placement and treatment of the center tap in common mode chokes.

Regarding resistors, I would go for standard low power, e.g. 0603 or 0805.
 

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