[SI-LIST] Re: [SI-LIST]EMI from two systems
- From: "Kai Keskinen" <kalevi@xxxxxxxxxx>
- To: <Charles.Grasso@xxxxxxxxxxxx>, <boris.traa@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>, <si-list-bounce@xxxxxxxxxxxxx>
- Date: Wed, 17 May 2006 17:37:36 -0400
Boris:
As an EMC guy from a previous incarnation, I would say you try to find the
clock frequency that you are seeing harmonics from, and then go to which
board contains it. Add a series ferrite barnacle to one of the clock
outputs. If it changed the amplitude vs frequency profile for the harmonics,
you probably found your culprit. Lots of other things you can try. The
spectrum analyzer plot can tell you a whole lot if you understand the two
systems. Some of the SI tools with EMC bolt-ons let you generate harmonic
profiles from the devices on the board. Some let you generate the
power/ground noise profiles from chips on the board. This way you can try to
isolate it without messing with the two systems but the real proof is in the
hardware. If the noise is from a switching supply, you have a whole other
problem but diagnostics are similar. You also try to understand the reason
you have a CM current from 1 floating box to another. The cable has a
ground. Is it connected at both ends with low inductance? Lots of
possibilities.
Enjoy!
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Grasso, Charles
Sent: Tuesday, May 16, 2006 7:05 PM
To: boris.traa@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx;
si-list-bounce@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: [SI-LIST]EMI from two systems
At this point you hire an experience EMC Engineer and throw lots of
money at them!! :-)
Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Boris Traa
Sent: Tuesday, May 16, 2006 2:59 AM
To: si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx
Subject: [SI-LIST] [SI-LIST]EMI from two systems
In my opinion EMC and SI are related topics. For that reason I woul like
to posit the following problem.
Assume two battery supplied systems A and B are connected to each other=20
via just one digital interface cable (e.g. USB) and positioned 80 cm
above=20
a reference plane. No more cables have been attached. If the EMI-level
of=20
this combination is to high I would like to investigate whether it is=20
system A or B. Switching A and B off alternately is no option because
it=20
will lead to a malfunction of the other system.=20
I could measure the CM-current through the interface cable but than I
can=20
not determine the main cause.=20
Who can offer me a nice idea?
Kind regards
Boris Traa
System design engineer EMC
It's the currents that make circuits work or fail.
Philips Applied Technologies/EM&C Competence Center
Room 1.024
High Tech Campus 26=20
5656AE Eindhoven, The Netherlands
Tel: ++ 31 40 27 43766
Fax: ++ 31 40 27 42224
E-mail: boris.traa@xxxxxxxxxxxx Seri: nlv09273@nlwayhp
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=20
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