Doug, I refer you to my reply of earlier where I cite pages in a book by Hall, Hall and McCall that gives a printed definition of ringback. Perhaps there are others. > [Original Message] > From: Douglas Burns <dburns@xxxxxxxxxx> > To: <leeritchey@xxxxxxxxxxxxx>; Madhusudhan Kulkarni <madhusudhan@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> > Date: 5/22/2006 12:26:27 PM > Subject: RE: [SI-LIST] Re: Ring back > > Lee, > > I would argue that overshoot and undershoot are specifying the same thing, > while ringback is it's own issue. Overshoot is how much a signal exceeds a > desired voltage level and is generally associated with VDD and VSS. Thus a > signal is in an overshoot condition when it exceeds VDD (or VSS). I see > people call the event overshoot when the signal exceeds VDD and undershoot > when it exceeds VSS...but in reality.. The signal is overshooting the target > voltage, independent of VDD or VSS) > > Many vendors specifications specify AC and DC overshoot. The max DC voltage > a device can accept (example VDD+0.3V or VSS -0.3v) would be a DC overshoot > limit. In addition, some vendors provide a time and with another max voltage > spec (ie VDD + 1v for <= 2ns). This second spec would be an AC overshoot > spec. > > Ringback on the otherhand does not require a signal to overshoot. Ringback > occurs when a signal makes multiple crossings of a voltage threshold and > affects timing margins. Use some standard LVTTL logic. Thresholds are 0.8V > and 2.0V. If a rising signal exceeds 2.0V, the signal is said to have > switched. If however, the signal crosses 2.0V, rises to 3.0V (below VDD of > 3.3)and then falls below 2.0 and then some time later crosses 2.0V and > settles out, when is the signal valid from a timing perspective. Based upon > worst case, it would be the second crossing. The ring between the 1st and > 2nd crossing is called ringback. Ringback occurs on both rising and falling > edges. > > To help reduce the uncertainty in timing points caused by ringback, vendors > have added AC and DC switching levels. A signal must than cross the AC > level, but is allowed to ringback to the DC level without effecting the > device timing. > > The IBIS specification does a good job documenting these events. > > Douglas J Burns > Vice-President, Consulting Services > Signal Integrity Software, Inc. (SiSoft) > 6 Clock Tower Place > Suite 250 > Maynard, MA 01754 > 978-461-0449 x14 > dburns@xxxxxxxxxx > > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On > Behalf Of Lee Ritchey > Sent: Monday, May 22, 2006 11:02 AM > To: Madhusudhan Kulkarni; si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Ring back > > > Ringback is just another name for undershoot. I don't know why someone had > to invent another name for something that already had a name. > > When you have undershoot and you use series terminations, the terminator > value it too high or the output impedance of the driver is too high. When > you have undershoot and you use parallel terminations, the value of the > terminator is too low. Fix which ever problem you have by changing the > value appropriately. > > > > [Original Message] > > From: Madhusudhan Kulkarni <madhusudhan@xxxxxxxxxx> > > To: <si-list@xxxxxxxxxxxxx> > > Date: 5/22/2006 9:28:26 AM > > Subject: [SI-LIST] Ring back > > > > Hi, > > How to solve ringback problem and what is the disadvantages of > > ringback > > ------------------------------------------------------------------ > > 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 > > ------------------------------------------------------------------ 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