[SI-LIST] Re: 自动回复: Emission Problem with Ethernet

  • From: Ram Chundru <rchundru_umr@xxxxxxxxx>
  • To: deepak Engineer <deepaksiengg@xxxxxxxxx>, si-list@xxxxxxxxxxxxx
  • Date: Wed, 22 Sep 2010 13:45:08 -0700 (PDT)

Hi Deepak,
To answer your first question, the 2kV high voltage rating on the capacitor is 
for protection from ESD/surge type events and it has no effect on radiated 
emissions.
You saw worse results with a 0 Ohm resistor than solder probably due to the 
higher inductance (ESL and mounting inductance) of the 0 ohm resistor. 
 Thanks,
Ram Chundru
EMC Engineer
Apple Inc.





________________________________
From: deepak Engineer <deepaksiengg@xxxxxxxxx>
To: si-list@xxxxxxxxxxxxx
Sent: Wed, September 22, 2010 8:27:22 AM
Subject: [SI-LIST] Re: è?ªå?¨å??å¤?: Emission Problem with Ethernet

Hello Experts,
To control the Emmision from Ethernt port, now I am using a two seprate
ground.

My question is:
1. How 1nf, 10v and 1nf,2kv will make a difference in EMI test. I had only
1nf, 10V smd capacitor available, but it gives 4bd spike above the margin.
do you think that for Emission test the voltage rating is important? I
though it will improve the emission transition but not making any
difference.
2. Similarly if I try a 0ohms then I am getting better result compare to
capcitor...below the margin -1.88db
but if I am shorting the two plane with solder then again I am getting a 2db
spike above the margin.
here what are the advantage of 0ohms vs solder..??

what is the best option, 1nf or 0ohms or solder ?
what will help for ESD protestion?

from previous discussion of Daniel, I can see 1nf as a solution, but
pratically 0ohms is giving a better result.

thanks in advance,
Deepak



2010/9/18 <aub4362@xxxxxxxx>

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