[SI-LIST] Re: Differential signals - skew - and EMC
- From: "Orin Laney" <olaney@xxxxxxxxx>
- To: <Charles.Grasso@xxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 1 Nov 2013 12:50:53 -0700
"It depends..." Skew to risetime ratio is the applicable metric. Keep it
low, say 0.1 as a target limit. The larger the number the worse life is.
Anything >1 = maximum bad. Regulatory effect depends on how much margin you
have to begin with. Let's just say that many projects have "negative
margin" on the first try at the test lab. Good design practice includes
common mode chokes on the PCB from the get go, rather than having to
retrofit cables with ferrites after you fail. It's cheap insurance.
Orin
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Grasso, Charles
Sent: Friday, November 01, 2013 12:32 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Differential signals - skew - and EMC
Hello,
In an ideal situation differential signals will have no skew through the
transmission path and (as I understand it) the common-signal (emi) will be
very low as a result. Given that EMC is very system dependent - does any
one have a rule of thumb or anxiety(!) factor for how much is skew is
tolerable before becoming an emissions (regulatory) Issue?
Thanks in advance.
Charles Grasso
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