Forums

ethernet magnetics

Started by John Larkin October 12, 2012
Has anyone examined the actual wideband time-domain coupling behavior,
like risetime and droop, of typical 10/100 Ethernet magnetics? I plan
to try a couple that we have in stock, but I was wondering if anyone
else has experience. We're considering using them in a non-Ethernet
data coupling situation.


-- 

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
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John Larkin wrote:
> Has anyone examined the actual wideband time-domain coupling behavior, > like risetime and droop, of typical 10/100 Ethernet magnetics? I plan > to try a couple that we have in stock, but I was wondering if anyone > else has experience. We're considering using them in a non-Ethernet > data coupling situation. > >
if they work, they have to be able to handle the LIT pulses. http://en.wikipedia.org/wiki/Autonegotiation "They are unipolar positive-only electrical pulses of a nominal duration of 100 ns, with a maximum pulse width of 200 ns," You should be able to work backwards from that for the risetime. -- Les Cargill
On 2012-10-12 18:38, John Larkin wrote:
> Has anyone examined the actual wideband time-domain coupling behavior, > like risetime and droop, of typical 10/100 Ethernet magnetics? I plan > to try a couple that we have in stock, but I was wondering if anyone > else has experience. We're considering using them in a non-Ethernet > data coupling situation. > >
Apparently, the Gigabit Ethernet specs require 350uH or more winding inductance. That should give you the droop. In a Coilcraft datasheet of the HPX2126L I found a graph that shows the upper frequency cut-off to be a little over 100MHz in a 100 Ohm setup, so the leakage inductance should be in the 150nH ballpark. That should give the risetime. There are some more plots, and maybe one of those gives some clue about inter-winding capacitance, but it's nearly midnight here and tomorrow is going to be a long day... Jeroen Belleman
"Jeroen" <jeroen@nospam.please> wrote in message 
news:k5a30l$7i6$1@speranza.aioe.org...
> Apparently, the Gigabit Ethernet specs require 350uH or more > winding inductance. That should give you the droop. In a > Coilcraft datasheet of the HPX2126L I found a graph that > shows the upper frequency cut-off to be a little over 100MHz > in a 100 Ohm setup, so the leakage inductance should be in > the 150nH ballpark. That should give the risetime.
I've measured some "10/100"s before, finding inductance about that. I forget what I found for leakage. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms