For a clock, I prefer capacitive coupling over Thevenin as it attenuates supply noise below the cutoff, which can be helpful for jitter reduction. Regards, Steve. At 02:57 PM 8/28/01 -0700, D. C. Sessions wrote: >On Tuesday 28 August 2001 14:40, ruston, matt wrote: > > > Does anyone know of an SSTL2 clock driver that accepts PECL inputs > (without > > having to shift the differential clk input levels)? I'm looking at > something > > like the TI CDCV850. Does anyone have any experience with this chip? Thanks > > for the help... > >I don't see the problem with shifting. PECL (at least the 3.3v version) >has an output common mode voltage of 1.98 v. SSTL-2 has an input >common mode of 1.25 v. Since you have to terminate anyway, why >not just terminate the SSTL-2 inputs to Vtt and connect the PECL >outputs through blocking caps? > >Alternately, you can just divide down with Thevenin networks. >Not perfect, but for two lines no big deal and 500 mV is plenty >for SSTL-2 inputs. > >-- >| The race is not always to the swift, nor the battle to the strong. | >| Because the slow, feeble old codgers like me cheat. | >+--------------- D. C. Sessions <dcs@xxxxxxxxxxxxxxxx> --------------+ >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field >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 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