How would you get common-mode noise rejection by using differential routing on a PCB with GND planes? One requirement for common mode noise rejection is equal and opposite EM fields. This is impossible in a common PCB structure where the GND plane is beneath or above AND beneath the differential signals. I do understand how you can obtain common-mode noise rejection in a cable...but in a PCB, I'm not so sure. Chris Landrum PCBA Design Engineer Maxtor Corporation -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Brown, Mike (Austin, TX) Sent: Wednesday, June 30, 2004 11:42 AM To: Aubrey_Sparkman@xxxxxxxx; weirsp@xxxxxxxxxx; gopalak@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: diff pair signal=20 In many board geometries, the coupling between "differential pairs" approaches zero. You are really dealing with two single-ended signals that happen to be complements of each other. It is possible to use one side of such a "differential pair" as a single-ended signal source. Assuming, for the moment, that you don't care about common-mode noise rejection at the receiver, and that you can generate a reference voltage that does not introduce too much duty-cycle distortion in the recovered signal. It's generally not a good practice, IMO. Mike -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Aubrey_Sparkman@xxxxxxxx Sent: Wednesday, June 30, 2004 10:26 AM To: weirsp@xxxxxxxxxx; gopalak@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: diff pair signal=3D20 I don't know of an actual instance where anyone has done this... BUT, for "other logical interfaces", one might attach a single ended sampler or detection circuit off one side IF (and big IF) acceptably isolated with high impedance resistor or whatever. Of course, SI work would need to be done to insure the loading would be acceptable to the diff pair interface. Aubrey Sparkman=3D3D20 Enterprise Engineering Signal Integrity Team Dell, Inc.=3D3D20 Aubrey_Sparkman@xxxxxxxx=3D3D20 (512) 723-3592 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir Sent: Wednesday, June 30, 2004 10:12 AM To: gopalak@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: diff pair signal=3D3D20 In such a situation where do you think the diff amplifier will obtain its=3D3D20 reference? At 07:38 PM 6/30/2004 +0530, Gopalakrishnan Sethuraj wrote: >Hello > > >Is there any scenario where one (positive) of the differential=3D20 >pair=3D3D20 signal output will be connected to single pin in LVDS or = =3D other >logical >interfaces ? > > > > > >Thanks&Regards > >Gopalakrishnan > > > > >------------------------------------------------------------------ >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:=3D3D20=3D20 >//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: =3D3D20 //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 =3D3D20 ------------------------------------------------------------------ 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: =3D20 //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 =3D20 ------------------------------------------------------------------ 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: =20 //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 =20 ------------------------------------------------------------------ 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