[SI-LIST] Re: EMI Ring in PCB

Hi Bill and the group,

In general, an ESD ring causes as many problems as it attempts to fix. 
I would not recommend using them and certainly not connecting them to 
chassis ground through a backplane connector. That just inserts lots 
of ESD noise into the sensitive signals in the backplane.

It would take a couple of pages of typing to adequately discuss how to 
handle ESD currents, here is a couple of major points (individual 
exceptions may apply):

-Isolating circuit boards from the chassis except through one point, 
generally increases ESD problems and forms a great tuned circuit 
(parallel plate capacitor from board and chassis and inductance of the 
signal connection). There are a few articles on my site at 
http://www.dsmith.org on this.

-Keep the ESD off the board entirely either through insulation or a 
metal faceplate robustly connected to chassis.

-ESD can generate hundreds of Volts/inch as it flows on a wire or 
circuit board trace. Even a tiny fraction of the coupled into nearby 
paths can spell disaster.

Lots more, but out of time. I have to finish loading up the equipment 
into the minivan for my teaching next week .

Doug

Bill Wurst wrote:

> Jongbae,
> 
> I believe you may have confused ESD with EMI.  If that is the case, I 
> would refer you to Chapter 12 in "Noise Reduction Techniques in 
> Electronic Systems" (2nd edition) by Henry W. Ott, and in particular, 
> Figure 12-17 on p.343.
> 
> Best regards,
>      -Bill
> 
> 
>        /************************************
>       /         billw@xxxxxxxxxxx         /
>      /                                   /
>     / Advanced Electronic Concepts, LLC /
>    /           www.aec-lab.com         /
>    ************************************
> =======================================================
> jbtera77@xxxxxxxxx wrote:
> 
>>Hi, all
>>Do anybody know about EMI ring and its effect?
>>
>>If someone recomment any document or paper which demonstrates EMI ring in
>>PCB, it will be very helpful.
>>
>>Thanks in advance,
>>Jongbae Park.
>>
>>
>>
> 
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