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AH1310- Application hints

Question asked by Liping Ren on Apr 6, 2017

Hi NXP customer support,

I have a question regarding AH1310- Application hints of “TJA1100 Automotive Ethernet PHY”. Section 3.4.5 Common mode termination on Page 18 indicates that “To provide some common mode termination of the channel, a split termination consisting of two resistors and a capacitor can be optionally connected to the signal lines between the coupling capacitors and the connector. For symmetry reasons the tolerance of the two resistors shall be within ±1%. The power rating of the resistors should be higher than 0.4W, depending on expected RF power in the actual application.”

I wonder larger than 0.4W specified here for resistor is the DC power or under AC. Why this power is needed?