COMMON-NOISE

Slide11IEEE802.3afNov.2000DTEPOWERDIFFERENTIALNOISEANDCOMMON-MODEVOLTAGEREQUIREMENTTerryCobbSlide22IEEE802.3afNov.2000IntroductionToensurethatthePHYwilloperateaDTEpowerdifferentialnoiserequirementshouldbeincluded.InadditionaCommon-modevoltagerequirementshouldalsobeincluded.AttachedaretheNoiseandCommon-modevoltagerequirementsfor:10BASE-T,100BASE-TX,and1000BASE-T.Thedifferentialnoiseorcommon-modevoltagewhenoperatingwithDTEpowershouldnotexceedthoserequirements.Slide33IEEE802.3afNov.2000DifferentialNoise10BASE-T:14.4.4.2CrosstalknoiseThelevelofcrosstalknoiseonasimplexlinksegmentdependsonthelevelofthedisturbingsignal(s)andthecrosstalklossbetweenthepair(s)carryingthesignal(s)andthedisturbedpair.Withthemaximumtrans-mitlevel(14.3.1.2),thesinusoidalcrosstalkloss(14.4.3.2),andmultiple,randomManchester-encodeddis-turbers,thepeakself-crosstalknoiselevelsasmeasuredattheoutputofthefollowingspecifiedfiltershallbelessthanorequalto264mV.Thefilterisa3-poleButterworthlow-passwitha3dBcutoffat15MHz(refertoB.4.2).100BASE-TX:25.4.6.3.1ExternalcouplednoiseThedifferentialnoisecoupledfromexternalsourcesthatismeasuredattheoutputofafilterconnectedtotheoutputofthenearendofadisturbedlinksegmentshallnotexceed40mVpeak-to-peak.ThefilterforthismeasurementisafifthorderButterworthfilterwitha3dBcutoffat100MHz.1000BASE-T:40.7.6ExternalcouplednoiseThenoisecoupledfromexternalsourcesthatismeasuredattheoutputofafilterconnectedtotheoutputofthenearendofadisturbedduplexchannelshouldnotexceed40mVpeak-to-peak.ThefilterforthismeasurementisafifthorderButterworthfilterwitha3dBcutoffat100MHz.Slide44IEEE802.3afNov.2000Common-modeVoltage10BASE-T:14.3.1.2.5Common-modeoutputvoltageThemagnitudeofthetotalcommon-modeoutputvoltageofthetransmitter,Ecm,measuredasshowninFig-ure14-14,shallbelessthan50mVpeak.NOTE-ThisspecificationisnotintendedtoensurecompliancewithregulationsconcerningRFemissions.Theimple-mentorshouldconsideranyapplicablelocal,national,orinternationalregulations.Drivingunshieldedtwistedpairswithhigh-frequency,common-modevoltagesmayresultininterferencetootherequipment.100BASE-TX:Norequirement.1000BASE-T:40.8.3.3MDIcommon-modeoutputvoltageThemagnitudeofthetotalcommon-modeoutputvoltage,Ecm_out,onanytransmitcircuit,whenmeasuredasshowninFigure40-32,shallbelessthan50mVpeak-to-peakwhentransmittingdata.47.5Ohms47.5Ohms49.9OhmsPHYEcmFigure14-14and40-32Slide55IEEE802.3afNov.2000ConclusionRecommendthefollowingrequirements:Differentialnoisevoltage:ThedifferentialnoisecoupledfromaDTEpowersourceshallnotexceed20(TBD)mVpeak-to-peakmeasuredatthedifferentialinputoftheMDIreceiverport(s).Common-modevoltage:WithDTEpowerappliedthemagnitudeofthetotalcommon-modeoutputACvoltageshallnotexceed50mVpeakwhenoperatingat10Mbit/sand50mVpeak-to-peakwhenoperatingat100Mbit/sorgreatermeasuredattheMDItransmitterport(s).Themagnitudeofthecommon-modeACvoltageshallnotexceed50mVpeak-to-peakmeasuredatallotherports.