creepage/clearance distances for LAN connection

[mcgyvr]

I need to know what are the required creepage and clearance distances on the traces of a PCB from the LAN isolation transformer to the RJ45 jack (IEC60950 requirements).

Im limited in my knowledge of this type of circuit and our reviewers (not sure if they are even qualified or understand what they are doing) at UL are requiring 1.24mm.
Is that correct?

I have the standard but just don't understand what type of circuit/insulation category it falls under. The board was designed by an outside firm and they have fallen off the face of the earth as soon as problems started popping up.

Thanks in advance

 

[mcgyvr]

Here is the schematic of the circuit in question

http://www.trimminc.com/brian/images/smm lan schem.jpg

 

[MacGyverS2000]

Don't quote me on this, but I can't imagine the clearance needing to be too great. I use RJ45 jacks with integrated magnetics, so the distance between the jack and isolation transformer is somewhere in the negative distance range.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[mcgyvr]

Im talking about the creepage/clearance (spacing between two traces next to each other) between the traces coming off the transformer to the jack.
Not the physical distance between the isolation transformer and the jack.

I always thought that the creepage/clearance was for 2 seperate circuits (ie a high voltage side of a TV and its associated 120V power supply),etc.. They are saying that the creepage/clearance even applies to everything, even the circuit I showed above.

Frankly I think they are crazy but I need some electrical background/facts to prove them wrong.

 

[MacGyverS2000]

Ah... it's low voltage, low current, so there's no rule on clearance between those tracks (only for those tracks and other higher-voltage surrounding tracks). You want each pair to be as close to each other as they're differential pairs and you don't want to have a large loop (i.e., antenna) in there.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[MacGyverS2000]

Oh, I should also mention you may want to keep each pair separated a bit, but it's nowhere near critical at those lengths.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[itsmoked]

I concur with Dan's assessment. And, in fact, yours.

You will find it hard or impossible to find a spec that sez "you can't do something". As apposed to, "you must do this".

Since this isn't a correct application of creepage worries, you won't find anything regarding it. IMHO.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com