[SI-LIST] Re: Question about split gnd planes

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: manickavelu_m@xxxxxxxxxxxx,<istvan.novak@xxxxxxxxxxx>, "Ed Troy" <etroy@xxxxxxxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
  • Date: Fri, 26 May 2006 04:17:08 -0700

Manix, no.  There are many misconceptions out there about the myth of 
ground and its relation to noise isolation.  Those myths get 
propagated into misguided applications of moats and such.  Think in 
fields and the misconceptions go away.

Steve.
At 09:50 PM 5/25/2006, Manickavelu M. wrote:
>Istan,
>Is it not that the analog and digital grounds planes can not be connected
>together anywhere but only under the chip that sources the analog signals?
>Also that while coupling these two planes we should not use direct Cu plane
>connection but couple them via inductors?
>
>Manix,
>MindTree.
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>Behalf Of istvan.novak@xxxxxxxxxxx
>Sent: Friday, May 26, 2006 6:26 AM
>To: Ed Troy; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Question about split gnd planes
>
>Ed,
>
>Splitting more than one ground plane in the stackup requires a lot of
>consideration, and mostly it is not necessary.  Isolating a sensitive circuit
>(e.g., analog input, low-jitter oscillator) may be a good idea, but instead
>of cutting a large solid ground plane, you may want to try first to put the
>circuit to be isolated on a grounded patch on a 'non-ground' layer.  You can
>make ground surface patches under and around your circuit to be isolated, or
>you can put the patch on a signal layer.
>
>Regards,
>
>Istvan Novak
>SUN Microsystems
>
>
>From: Ed Troy <etroy@xxxxxxxxxxxxxxx>
>Date: Thu May 25 15:38:33 CDT 2006
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Question about split gnd planes
>
>If you have a circuit board that requires a split gnd  plane over a
>small section of the board, and you have several ground planes,
>should only one have the split (the one nearest the side containing
>the components that require analog ground)  while the rest of the
>ground planes are continuous, or should the split section be on all
>ground layers? I would think that you should only have it on one
>layer. Also, if it should only be on one layer, I would imagine it
>would be best to connect it to the digital ground with one, and only
>one, via. Is that generally correct? What are some good references
>for layer stackups, etc? I know I saw one, once, but can't remember where.
>
>Ed
>
>
>------------------------------------------------------------------
>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:
>//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?Si-List_FAQ
>
>List technical documents are available at:
>                 http://www.si-list.org
>
>List archives are viewable at:
>                 //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
>
>
>------------------------------------------------------------------
>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:
>//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?Si-List_FAQ
>
>List technical documents are available at:
>                 http://www.si-list.org
>
>List archives are viewable at:
>                 //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
>
>
>
>-- Attached file included as plaintext by Ecartis --
>-- File: disclaimer.txt
>
>-----------------------------------------------------------------------------------------------------------------------------
>Disclaimer
>-----------------------------------------------------------------------------------------------------------------------------
>
>"This message(including attachment if any)is confidential and may be 
>privileged.Before opening attachments please check them
>for viruses and defects.MindTree Consulting Private Limited 
>(MindTree)will not be responsible for any viruses or defects or
>any forwarded attachments emanating either from within MindTree or 
>outside.If you have received this message by mistake please notify 
>the sender by return  e-mail and delete this message from your 
>system. Any unauthorized use or dissemination of this message in 
>whole or in part is strictly prohibited.  Please note that e-mails 
>are susceptible to change and MindTree shall not be liable for any 
>improper, untimely or incomplete transmission."
>
>-----------------------------------------------------------------------------------------------------------------------------
>
>------------------------------------------------------------------
>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:
>//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?Si-List_FAQ
>
>List technical documents are available at:
>                 http://www.si-list.org
>
>List archives are viewable at:
>                 //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
>

------------------------------------------------------------------
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:
//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?Si-List_FAQ

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

List archives are viewable at:     
                //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: