PCIE 布线规范

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1、MCS9901PCBLayoutPCBLayoutGuideLinesGuidelines1.IntroductionAssystemoperationspeedsareincreasing,PCBlayoutisbecomingincreasinglycomplex.Asuccessfulhigh-speedlayout/PCBneedtointegratetheIC’sandotherperipherals/componentseffectivelyintoasingledesign.MCS9901hasPCIe,Serial,Parallel,ISA&USBinterfacesandut

2、ilizefastI/Opinswithedgeratesthatarelessthanahundredpicoseconds.AsFastedgeratescancontributetonoisegeneration,signalreflection,cross-talkandgroundbounce;SystemdesignersmustbecarefulinhandlingtheseissuesduringPCBlayoutdesign.ThisdocumentprovidesgenericlayoutguidelinesforMCS9901basedproducts.PCIeto4Se

3、rialevaluationboarddesignusedasanexampletodetailtheguidelinesbelow.2.PCBOverview2.1.1.PCBDetailsFigure1aistheTopsideoftheMCS99014SerialBoard.MostofthecomponentsareplacedontheTopsideofthePCB.Supplydecouplingcapacitorsusedonthebottomsidetoarriveatsmallformfactor.Customerswishingtohavecomponentsonlyoft

4、opsideforprocess&costreasonscandoso,withappropriatelayout.Figure1a-TopSideViewofMCS9901-4S-EVBthRev1.1Preliminary-1-26Nov2007MCS9901PCBLayoutPCBLayoutGuideLinesGuidelinesFigure1bTopSideView-ComponentPlacementMCS9901-4S-EVB2.2ComponentsPlacementA.MCS9901ASICB.12MHzCRYSTALC.SERIALPORTSthRev1.1Prelimin

5、ary-2-26Nov2007MCS9901PCBLayoutPCBLayoutGuideLinesGuidelines3.LayoutGuidelinesThislayoutguidediscussestheimportantissuesandprovideguidelinesforsuccessful,effectivepcbdesignsusingMCS9901.•PCIe_REFCLKP&PCIe_REFCLKN,PCIe_TXP&PCIe_TXN,PCIe_RXP&PCIe_RXNarethe3differentialpairstoberoutedfromPCIeedgeconnec

6、tortoMCS9901ASICwith100OhmsdifferentialImpedance.•USB-DP&USB-DMaredifferentialpairstoberoutedwith90OhmsdifferentialImpedance,thisruletobeappliedforUSBflavorofMCS9901EVB.•Generallayoutguidelines3.1.1.PCIe,USB&GenericLayoutGuidelinesMCS9901PlacementandPCIeRoutingGuidelines•PlacetheMCS9901ASICascloseas

7、tothePCIeconnectorontheboardasshowninFigure1b.•KeepparallelismbetweenPCIe_REFCLKP&PCIe_REFCLKN,PCIe_TXP&PCIe_TXN,andPCIe_RXP&PCIe_RXNwiththetracespacing,commontracewidth/lengthstoachieve100Ohmsdiffere