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power comsumption in RJ45 jacks with common mode

Discussion in 'Electronic Basics' started by John, Feb 11, 2005.

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  1. John

    John Guest

    I am taking over a design that I don't know too much about. It's a
    network card that has an RJ45 jack with integrated magnetics. The
    RJ45 has a CMT pin that is connected to 2.5V through some discretes.
    What does this pin do? Is it a common mode tap? What does that mean?
    What I really need to know is, does this pin consume any power?

    Thanks, John
     
  2. John

    John Guest

    I did attempt to figure this out. I spent a week googling comon mode,
    CMT, transformer, rj45, etc. I just didn't find any basic answer that I
    understood. I could ask the vendor AE, but sometimes I don't want to
    let them know how much I still need to learn....

    John
     
  3. Could it be for Power Over Ethernet?

    http://www.hyperlinktech.com/web/what_is_poe.php
     
  4. peterken

    peterken Guest

    uh ?
    I know of
    http://www.fciconnect.com/pdffiles/datasheets/950528-015.pdf
    http://www.filtran.com/filtran/datasheets/8305.pdf

    but does your design have an active component inside the connector ?
    never heard of something like that...

    or is it more alike the schematics on
    http://www.intel.com/design/network/applnots/75222801.pdf

    checkout the discrete part, might just be some ground thing
     
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