In the picture I sent you the entire solid red line is the join. I think trying to DC isolate common through DVI with capacitors is a mistake. Steve. qantrix wrote: > OK. I understood. It will provide connection with lowest impedance. > H.Ott write about it in his book. > Did you connected it on all layers or outer only? > If i don't want DC flowing through my chassis - i need to connected it > to gnd in each point with few capacitors 10n, 1n, 100pf in parralel? > > > 2010/5/6 Grasso, Charles <Charles.Grasso@xxxxxxxxxxxx>: > >> We have several designs that are laid out just like Steve is recommending. >> Do not add moats where they are not needed. >> >> Also - I would NOT add the internal shields to the chassis ground at the I/O. >> This is an ideal way of letting EMI out and cause immunity problems. >> >> ________________________________________ >> From: si-list-bounce@xxxxxxxxxxxxx [si-list-bounce@xxxxxxxxxxxxx] On Behalf >> Of steve weir [weirsi@xxxxxxxxxx] >> Sent: Tuesday, May 04, 2010 7:34 AM >> To: qantrix >> Cc: si-list@xxxxxxxxxxxxx >> Subject: [SI-LIST] Re: CHGND connection in DVI connector >> >> I disagree with the recommended design. >> >> I would connect signal and chassis grounds through a peninsula at the >> chassis side of the DVI connector. Depending on what else is going in >> and out of the box, bonding at other locations would also be >> appropriate. At a minimum you need to do it at the DVI connector. The >> basic premise is to reduce antenna efficiency and reduce energy pumped >> into the antenna. Big loops make for efficient antennas. Extending the >> chassis ground into the main PCB while still moating from signal ground >> is likely going to create coupling issues that will bite you, never mind >> the SI degradation you will get from crossing the moat. >> >> Much has been written on this area of interest. Doug Smith has a number >> of short articles and demonstrations showing how various grounding >> schemes work and fail. >> >> Steve. >> qantrix wrote: >> >>> Steve, >>> >>> http://img504.imageshack.us/i/currentdesign.png/ >>> you can find current design. data(diff.pairs) shield connected to sgnd. >>> >>> suggested design see here >>> http://img266.imageshack.us/i/suggested.png/ >>> >>> As you can see ch_gnd will cover all area of dvi connector and pins of >>> data pairs shield connected to ch_gnd. >>> diff.pairs will pass under separation between planes. >>> >>> Idea make it like this seems like bad. >>> >>> But it's possible to connect pairs shield to ch_gnd without creating >>> slot under pairs and cable will have only quite ch_gnd shield for each >>> pair and not dirty sgnd. Question is - does this shield carrying >>> return currents ? How it will work from EMC point ? >>> >>> >>> >>> 2010/5/4 steve weir <weirsi@xxxxxxxxxx>: >>> >>> >>>> Is there a reason you want to isolate signal common from chassis? Common >>>> practice is to join the two near the chassis boundary. If you attempt to >>>> isolate them, you will have lots of capacitive sneak paths. If they are >>>> joined you will not have a CM discontinuity issue. >>>> >>>> Steve. >>>> >>>> qantrix wrote: >>>> >>>> >>>>> I have question about CHGND connection in DVI connector/cable. >>>>> There is two kind of shields - one - is shield for data/clock pair; >>>>> second - whole cable shield. >>>>> http://en.wikipedia.org/wiki/Digital_Visual_Interface >>>>> >>>>> We had some EMC consultation - was suggested to connect internal pairs >>>>> shield to chgnd. >>>>> on pcb make polygone chgnd that cover area up to end of dvi connector. >>>>> So diff.pairs will run under slot of gnd.separation. >>>>> >>>>> Question is - how should be connected internal shields in DVI >>>>> conenctor - to sgnd or to chgnd? >>>>> >>>>> diff. pairs running on the slot - seems like bad idea? >>>>> ------------------------------------------------------------------ >>>>> 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 technical documents are available at: >>>>> http://www.si-list.net >>>>> >>>>> List archives are viewable at: >>>>> //www.freelists.org/archives/si-list >>>>> Old (prior to June 6, 2001) list archives are viewable at: >>>>> http://www.qsl.net/wb6tpu >>>>> >>>>> >>>>> >>>>> >>>>> >>>> -- >>>> Steve Weir >>>> IPBLOX, LLC 150 N. Center St. #211 >>>> Reno, NV 89501 www.ipblox.com >>>> >>>> (775) 299-4236 Business >>>> (866) 675-4630 Toll-free >>>> (707) 780-1951 Fax >>>> >>>> >>>> >>>> >>>> >>> ------------------------------------------------------------------ >>> 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 technical documents are available at: >>> http://www.si-list.net >>> >>> List archives are viewable at: >>> //www.freelists.org/archives/si-list >>> >>> Old (prior to June 6, 2001) list archives are viewable at: >>> http://www.qsl.net/wb6tpu >>> >>> >>> >>> >>> >> -- >> Steve Weir >> IPBLOX, LLC >> 150 N. Center St. #211 >> Reno, NV 89501 >> www.ipblox.com >> >> (775) 299-4236 Business >> (866) 675-4630 Toll-free >> (707) 780-1951 Fax >> >> >> ------------------------------------------------------------------ >> 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 technical documents are available at: >> http://www.si-list.net >> >> List archives are viewable at: >> //www.freelists.org/archives/si-list >> >> Old (prior to June 6, 2001) list archives are viewable at: >> http://www.qsl.net/wb6tpu >> >> >> ------------------------------------------------------------------------ >> -- Steve Weir IPBLOX, LLC 150 N. Center St. #211 Reno, NV 89501 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu