power comsumption in RJ45 jacks with common mode

[John]

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

 

[John]

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

 

[Anthony Fremont]

"John" <josepugmima@comcast.net> wrote in message
news:1108150075.279418.49960@f14g2000cwb.googlegroups.com...

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....

Could it be for Power Over Ethernet?

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

 

[peterken]

"John" <josepugmima@comcast.net> wrote in message
news:1108122278.420980.178070@c13g2000cwb.googlegroups.com...

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

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