Ben Rothchild wrote: > Vinu, > > Thanks for the input. I forgot to mention > in my last mail that all these links are > differential PECL. Any idea what is run length > for 155-STM1 and 622-STM4. I am not familiar with these transmission standards. > The 1.25G and > 2.5G are 8B/10B coded so run lengths should not > exceed 8. > > The value recommended for the AC coupling cap > is 0.01uF. Now with an ESL of say 4nH > we have w=1/(0.01uF X 4nH)^0.5=500Mhz > for the case of series resonance, > or f=79Mhz. How is this going to work > for even 155M leave alone 1.25G/2.5G. > I seem to have got something wrong. Could > you or somebody correct me. > At 2.5Gbps, the series impedance is dominated by the mounted inductance of the capacitor. While the impedance of the capacitor is not at its lowest at this frequency, with proper layout/stackup, it will be low enough to work at 2.5Gbps. > > Thank you once again, > > Ben > --- Vinu Arumugham <vinu@xxxxxxxxx> wrote: > > > > Usually the AC coupling capacitor would need a > > couple of vias to connect > > to the lines. Reflections from this structure can be > > lowered by placing > > it near the receiver where the edge rate is slower > > than at the > > transmitter. > > > > If you do not have very long run lengths (>100 > > bits), a 0.01uF will > > work. > > > > Thanks, > > Vinu > > > > Ben Rothchild wrote: > > > > > Hello Experts, > > > > > > I have a question on AC coupling. > > > While AC coupling a high speed serial > > > link to match levels, where should > > > the AC coupling capacitor be placed. > > > Close to transmitter/close to receiver/ > > > or doesn't matter, can be placed > > > anywhere on the link. > > > > > > What should be the value of the AC > > > coupling capacitor or rather how > > > do I calculate it. Is it dependent on > > > frequency. I am trying to AC couple > > > signals of 155M, 622M, 1.25G and 2.5G. > > > Any special care to be taken at these > > > different frequencies. > > > > > > Thanks for any advice. > > > Ben > > > > > > __________________________________________________ > > > Do You Yahoo!? > > > Great stuff seeking new owners in Yahoo! Auctions! > > > http://auctions.yahoo.com > > > > > > ------------------------------------------------------------------ > > > 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 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 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 > > > > > > __________________________________________________ > Do You Yahoo!? > Great stuff seeking new owners in Yahoo! Auctions! > http://auctions.yahoo.com > ------------------------------------------------------------------ > 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 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 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