DM9000A-PCB板布线指南

DM9000A/9010LayoutGuideVersion:DM9000A/9010-LG-V101AUG19,2004DM9000A/9010LayoutGuideTechnicalReferenceManualBy:DAVICOMCharlesTsaiDavicomSemiconductor,IncDM9000A/9010LayoutGuide2Version:DM9000A/9010-LG-V10AUG19,20041.Placement,SignalandTraceRouting•Placethe10/100MmagneticascloseaspossibletotheDM9000A/9010(nomorethan20mm)andtotheRJ-45connector.•Placetheterminationresistors50ascloseaspossibletothe10/100MmagneticandtheDM9000A/9010RXpinsandTXpins.The50resistorsandgroundingcapacitorsofTXandRXshouldbeplacednearDM9161(nomorethan10mm).•The25MHzcrystalshouldnotbeplacednearimportantsignaltraces,suchasRXreceivepairandTXtransmitpair,bandgapresistor,magneticandboardedge.•TracesroutedfromtheDM9000A/9010RXpairtothe10/100MmagneticandtheRJ45connectorshouldrunsymmetrically,directly,identically,andclosely(nomorethan2mm).ThesameruleisappliedtotracesroutedfromtheDM9000A/9010TXpair.MagneticRJ-45RX+RX-TX+TX-d1d2d1d12mmd23mm;havingAGNDasashieldisbetterd35mm;havingAGNDasashieldisbetterd1d1d2Donotturnatrightangle(90),turn45insteadCrystald3betterMagneticRJ-45RX+RX-TX+TX-d1d2It’sworsetoturnatrightangle(90)Crystald3Worsed1WorseDM9000A/9010LayoutGuideVersion:DM9000A/9010-LG-V103AUG19,2004•ItisrecommendedthatRXreceiveandTXtransmittracesturnat45°angle.Donotturnatrightangle.BetterWorse•AvoidusingviasinroutingthetracesofRXpairandTXpair.•TheRXpair,TXpair,clock,andpowertracesshouldbeasshortandwideaspossible.•DonotplacetheDM9000A/9010RXreceivepairacrosstheTXtransmitpair.Keepthereceivepairawayfromthetransmitpair(nolessthan3mm).It’sbettertoplacegroundplanebetweenthesetwopairsoftraces.•Thenetworkinterface(seeFigure3-1andFigure4)doesnotrouteanydigitalsignalbetweentheDM9000A/9010RXandTXpairstotheRJ-45.Keepthetwopairsawayfromalltheotheractivesignalsandthechassisground.•Itshouldbenopowerorgroundplaneintheareaunderthenetworksideofthe10/100MmagneticandtheareaundertheRJ-45connector.•AnyterminatedpinsoftheRJ-45connector(pins4,5,7and8,seeFigure1)andthemagnetic(seeFigure1)shouldbetiedascloselyaspossibletothechassisgroundthrougharesistordividernetwork75resistors(nomorethan2mmtothemagnetic)anda0.01µF/2KVbypasscapacitor.•TheBandGapresistorshouldbeplacedascloseaspossibletopins47and48(BGRES,BGRESG)(nomorethan3mm).Avoidrunninganyhigh-speedsignalneartheBandGapresistorplacement(nolessthan3mmfrom25MHzXT1andXT2).DM9000A/9010LayoutGuide4Version:DM9000A/9010-LG-V10AUG19,2004DM9000A10Base-T/100Base-TXApplicationFigure1-1and1-2illustratethetwotypesofthespecificmagneticsinterconnectandhowtoconnectwithDavicomDM9000A.Thesemagneticsarenotpin-to-pincompatible.PleasemustbeconsideredwhenusingtheDM9000Ainauto-MDIXmode.Figure1-1Figure1-2DM9000A/9010LayoutGuideVersion:DM9000A/9010-LG-V105AUG19,2004DM901010Base-T/100Base-TXApplicationFigure1-3and1-4illustratethetwotypesofthespecificmagneticsinterconnectandhowtoconnectwithDavicomDM9010.Thesemagneticsarenotpin-to-pincompatible.PleasemustbeconsideredwhenusingtheDM9010inauto-MDIXmode.Figure1-3Figure1-4DM9000A/9010LayoutGuide6Version:DM9000A/9010-LG-V10AUG19,20042.PowerSupplyDecouplingCapacitors•PlaceallthedecouplingcapacitorsforallpowersupplypinsascloseaspossibletothepowerpadsoftheDM9000A/9010(nomorethan2.5mmfromtheabovementionedpins).Therecommendeddecouplingcapacitoris0.1µFor0.01µF.•ThePCBlayoutandpowersupplydecouplingshouldprovidesufficientdecouplingtoachievethefollowingwhenmeasuredatthedevice:(1)AllDVDDsandAVDDsshouldbewithin50mVppofeachother,(2)AllDGNDsandAGNDsshouldbewithin50mVppofeachother.(3)TheresultantACnoisevoltagemeasuredacrosseachDVDD/DGNDsetandAVDD/AGNDsetshouldbelessthan100mVpp.•The0.1-0.01µFdecouplingcapacitorshouldbeconnectedbetweeneachDVDD/DGNDsetandAVDD/AGNDsetandbeplacedascloseaspossibletothepinsofDM9000A/9010.TheconservativeapproachistousetwodecouplingcapacitorsoneachDVDD/DGNDsetandAVDD/AGNDset.One0.1µFisforlowfrequencynoise,andtheother0.01µFisforhighfrequencynoiseonthepowersupply.•TheAVDDconnectiontothetransmitcentertapofthemagnetichastobewelldecoupledtominimizecommonmodenoiseinjectionfromthepowersupplyintothetwistedpaircable.Itisrecommendedthata0.01µFdecouplingcapacitorshouldbeplacedbetweenthecentertapAVDDtoAGNDgroundplane.Thisdecouplingcapacitorshouldbeplacedascloseaspossibletothecentertapofthemagnetic.10uFor47uFCapacitorshouldbeconnectedbetweeneachAVDDandAGND.Figure2DM9000A/9010LayoutGuideVersion:DM9000A/9010-LG-V107AUG19,20043.GroundPlaneLayout•PlaceasinglegroundplaneapproachtominimizeEMI.GroundplanepartitioningcancauseincreasedEMIemissionsthatcouldmakethenetworkinterfacecard(NIC)notcomplywithspecificFCCpart15andCEregulations.•Groundplaneneedseparateanaloggrounddomainanddigitalgrounddomain,theanaloggrounddomainanddigitalgrounddomainconnectedlineisfarawaytheAGNDpinsofDM9000A/9010(seeFigure4-1).•AllAGNDpins(pin5,6,46)couldnotdirectlyshorteachother(seeFigure3-3).Itmustbedirectlyconnectedtoanaloggrounddomain(seeFigure3-2).•AnaloggrounddomainareaisaslargeaspossibleFigure3-1DM9000A/9010LayoutGuide8Version:DM9000A/9010-LG-V10AUG19,2004AnaloggrounddomainDigitalgrounddomainAGNDAGNDAGNDGoodAnaloggrounddomainDigitalgro