[SI-LIST] Fwd: Re: About the chassis gnd and logic gnd

>Date: Thu, 25 Mar 2004 07:52:24 -0800
>To: peter.zhu@xxxxxxxxxx, <si-list@xxxxxxxxxxxxx>
>From: steve weir <weirsp@xxxxxxxxxx>
>Subject: Re: [SI-LIST] About the chassis gnd and logic gnd
>
>Peter, the subject has been covered many times.  There are seemingly 
>religious views on this.
>
>I belong to the "reduce antenna gain" camp, which is to say that at high 
>frequencies, even an air gap does not effect isolation, it just increases 
>antenna gain and ESD susceptibility.  So multipoint bonding is the 
>preferred strategy in my book.  Bond often, and bond well.  There is one 
>caveat, and that is if you have external low voltage power supplies, then 
>you have to watch the return current path.  But since you likely use 
>isolated DC-DC converters, this should not present an issue to you.
>
>This point of view is supported by practices at major successful 
>manufacturers such as Cisco where those practices resulted in behemoth 
>boxes like the 12000 that have no EMC issues at all.  It is also supported 
>by respected authors like Mark Montrose, and Doug Smith who show the 
>science behind why this practice works, as well as successful engineers 
>with many years experience like Chris Cheng.  My recollection is that John 
>Barnes covers this subject in his books as well.  If you can afford them, 
>and even if you can't, John brings many years experience including with 
>ultra cost sensitive consumer product.
>
>If you go to Doug Smith's web site, www.emcesd.com and look up his April 
>2002, May 2002, and October 2002 "Technical Tidbits" he demonstrates the 
>value of multipoint grounding very clearly for ESD immunity.
>
>Regards,
>
>
>Steve.
>At 07:43 PM 3/25/2004 +0800, peter zhu wrote:
>>all:
>>About the chassis GND and the logic GND, some company tie them together, and
>>some sompanies separate them.
>>In telecom equipments, I see many companies, such as NOKIA, tie them
>>together, and the backplane only has uniform GND layer for chassis gnd and
>>logic gnd. We separate them in our backplane, but it will result in PCB gnd
>>layer partition. So form the PCB view, we hope the uniform gnd.
>>What's the recommendation form the EMC/EMI view? and what's your company's
>>strategy?
>>
>>Thank,
>>
>>Peter
>>UTStarcom
>>
>>------------------------------------------------------------------
>>To unsubscribe from si-list:
>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>
>>or to administer your membership from a web page, go to:
>>http://www.freelists.org/webpage/si-list
>>
>>For help:
>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>
>>List FAQ wiki page is located at:
>>                 http://si-list.org/wiki/wiki.pl
>>
>>List technical documents are available at:
>>                 http://www.si-list.org
>>
>>List archives are viewable at:
>>                 http://www.freelists.org/archives/si-list
>>or at our remote archives:
>>                 http://groups.yahoo.com/group/si-list/messages
>>Old (prior to June 6, 2001) list archives are viewable at:
>>                 http://www.qsl.net/wb6tpu
>>
>
>Steve Weir
>Teraspeed Consulting Group LLC
>2926 SE Yamhill St.
>Portland, OR 97214
>(503) 239-5536
>http://www.teraspeed.com
>------------------------------------------------------------------------------------------------------
>Teraspeed(SM) is the service mark of Teraspeed Consulting Group LLC

Steve Weir
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
------------------------------------------------------------------------------------------------------
Teraspeed(SM) is the service mark of Teraspeed Consulting Group LLC


------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: