[SI-LIST] Re: ESD is a low frequency event -really??

Doug,

Quoted from your experimental results:
"One of the reasons cited for using a single board ground is to keep ESD
currents from flowing onto and off of the board. As can be seen, the board
coupling to the underlying metal plane is so strong the currents will flow
anyway and multiple connections can even reduce the board currents as shown
in Figure 4."

You have demonstrated benefit from the multiple grounding point design
approach to ESD mitigation.

Jim

_____________________
James L. Knighten, Ph.D.
Teradata, a division of NCR                 http://www.ncr.com
17095 Via del Campo
San Diego, CA 92127
tel: 858-485-2537
fax: 858-485-3788


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Doug Smith
Sent: Thursday, March 11, 2004 8:24 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ESD is a low frequency event -really??

Hi All,

Quite separately from individual design techniques cited on this 
subject, I would like to point out that there are so many parasitics 
involved in ESD response of a circuit. Just because a design technique 
worked a few times does not mean it worked for the reasons thought by 
the person involved.

To have a really good understanding of what is happening, one needs to 
set up a test case and measure induced EMI in a ciruit while changing 
one variable at at time. I have lost count of clients that did not 
have enough control over a set of troubleshooting experiments to be 
able to draw a valid conclusion.

Tests are not difficult to perform, but one must be careful and 
understand what the parasitics are. (2000 volts changing across 1 pF 
in a nanosecond generates 2 Amps of current!)

As an example of a simple experiment, take a look at:

http://emcesd.com/tt2002/tt050102.htm

that describes an experiment I did on a circuit board mounted over 
metal where the metal was subjected to ESD.

Can anyone report on experments like this in support of their 
positions? It is not enough to say "I used this design technique and 
it worked" unless you can explain carefully and in detail why it 
worked. Only then can the design technique be generalized to other cases.

Doug


Tom Biggs wrote:
> "I presume you can give us some real example of systems with proper
> stackup failing ESD test and when BC is added it 'magically'(sic) passed
> ?" "This is a simple yes or no answer."
> 
> -reply-
> 
> "Designs within these companies were aided in the=20
> correction of susceptibilities by the use of BC."
> 
> This sounds like a simple yes to me. Maybe you read it differently.=20
> 
> If you don't think it would work tell us why. I bet most of the readers
> on this list would be interested in hearing this, rather than hearing
> you attacking another list poster no matter how poorly you think he
> presents his case.=20
> 


-- 
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     ___          _       Doug Smith
      \          / )      P.O. Box 1457
       =========          Los Gatos, CA 95031-1457
    _ / \     / \ _       TEL/FAX: 408-356-4186/358-3799
  /  /\  \ ] /  /\  \     Mobile:  408-858-4528
|  q-----( )  |  o  |    Email:   doug@xxxxxxxxxx
  \ _ /    ]    \ _ /     Website: http://www.dsmith.org
-------------------------------------------------------

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