The definition is based on two parameters rise time and length f transmission line... when the length of the transmission lines becomes comparable with rise time, transmission line management has to be done. Critical length = ( rise time / 7 ) * ( C / sqrt (dielectric constant) ) i.e, = ( rise time / 7 ) * (velocity of signal propogation) e.g, if rise time = 1 ns, C L = 1 ns / 7 * 6 inch per ns = 0.85 inches... also, there is another definition...Based on crosstalk, CL is also defined as length at which backward crosstalk reaches maximum. i.e at CL = Transition electrical length / 2. i.e, CL = 3 inches for a rise time of 1 ns ( TEL = 6 inches for rise time =1 ns, in 1 ns signal travels approx. 6 inches on a pcb) On Mon, Sep 21, 2009 at 12:22 PM, Rama Mohan Reddy Boreddy < mohan.svuce@xxxxxxxxxxxxxx> wrote: > Hi, > Can anyone tell when a signal is considered as a high speed signal? Is > there any definition for high speed signal in time domain and frequency > domain? > > I know that a rise time and PCB trace/Interconnect legth is one of the > parameters to define a signal as high speed signal. Can any body provide me > the formula > > Can any body share a FAQ on high speed signals and Cross talk > > Regards, > Rama Mohan Reddy > > > ------------------------------------------------------------------ > 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 > 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 technical documents are available at: http://www.si-list.net 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