[SI-LIST] Re: E1/T1/E3/T3 requirements
- From: "Doug McKean" <dmckean@xxxxxxxxxxxxxxx>
- To: "Signal Integrity Group" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 14 Jan 2002 18:13:08 -0800
Depends upon what the voltage levels being used in the
applicable immunity and telephone standards for the product.
For air discharge breakdown, as a "Rule of Thumb" I use
1MV is 1 meter. 1KV is 1mm or 40 mils.
And 8Kv is ... well ... 8mm. And 12KV is, well, 12mm.
Very rough estimates. Tip geometry can greatly affect this.
All follows Paschen actually for temp and pressure.
Telco environs can be rough. Especially the Bellcore standards.
Hmmm ... 12KV sounds strangely similar to an average street
level power line voltage for a neighborhood which can run
anywhere from as low as 2.4KV to as high as 24KV with the
average about 12KV. Don't know. Just throwing out some
ideas which come to mind. Someone anticipating some
cross power condition like a telephone line crossing with
a power line? Interesting.
For sensitive inputs, I've been known to carefully calculate
the separations required by the standards, then compare those
separations needed to pass the levels of testing, then multiply
the whole thing by 2 for a double safety factor if I can get away
with it. But that's me.
Although 12mm sounds big, I'm not sure what levels the surge
and lightning tests might be. That would have to be checked.
Personally, the more separation you can give me, the better.
Even if I don't need it.
Regards, Doug McKean
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