ECE744DesignofElectronicPackagingandInterconnectClassSection1SignalIntegrityMeasurementsRobertJ.Evans,Ph.D.CiscoSystemsResearchTrianglePark,NorthCarolina27709Ph.(919)392-8430Fax(919)392-4537bob.evans@ieee.orgRobertJ.Evans,Ph.D.bob.evans@ieee.org1WhyDoWeNowCareMoreAboutSignalIntegrity?RobertJ.Evans,Ph.D.bob.evans@ieee.org2TimingsareCompressed1µsecDataCLK1nsDataCLKRobertJ.Evans,Ph.D.bob.evans@ieee.org3VoltageLevels,NoiseMarginsareCompressed5VihVil02.5Vih0VilRobertJ.Evans,Ph.D.bob.evans@ieee.org4WhyDoWeCareMoreAboutSignalIntegrity?•FasterSignalingAllowsLessTimeforNoiseConsiderations•SettlingTimes•Setup&HoldTimes•FasterSignalingRequiresSteeperSlopesonDriverOutputs•FrequencyContentisHigher,MoreHi-FEffects•VoltageSwitchingLevelsareDecreasing5-3.3-2.5-1.8-1.5-???•AllowsforLessNoiseMarginRobertJ.Evans,Ph.D.bob.evans@ieee.org5Frequency,Period,DutyCycleMid-LevelVoltageTotalTimePeriodFrequency=1/TotalTimePeriodDutyCycle=TimeAboveMidReference/TotalTimePeriodRobertJ.Evans,Ph.D.bob.evans@ieee.org6SignalHighTime,LowTimeHighTimeVih-minTransitionRegionVil-maxLowTimeFirstTransitionintoHighorLowRegionsRobertJ.Evans,Ph.D.bob.evans@ieee.org7RisingEdgeOvershootOvershootandRingbackRisingEdgeRingbackFallingEdgeRingbackFallingEdgeOvershootReferenceVoltage(Ground)RobertJ.Evans,Ph.D.bob.evans@ieee.org8InsertCADENCEScannedOver/UndershootPage(NotCorrect)OvershootandRingbackCourtesyofCADENCERobertJ.Evans,Ph.D.bob.evans@ieee.org9RiseandFallTimes90%S.S.Level10%S.S.LevelRiseTime(10-90%)FallTime(10-90%)Careful:Somecircuitsspecifiedat20%to80%forRise/FallTimes!RobertJ.Evans,Ph.D.bob.evans@ieee.org10ClockSkew•Occurswhendifferentdevicesseetheclocktransitionatdifferenttimes•Increases/decreasestheapparentclockcycle.Dependingonwhichdevicesaredriving/receiving•ReducestheeffectiveclockcycleClockt=0Drivert=1D0D1D2t=2D0D1D2CourtesyofCADENCERobertJ.Evans,Ph.D.bob.evans@ieee.org11TimingSkewNegativeSkewReferenceClockPositiveSkewData&StrobeReceiverCourtesyofIntelCorp.RobertJ.Evans,Ph.D.bob.evans@ieee.org12ClockJitterLongTermJitterVccMidReferenceGroundCourtesyofIntelCorp.RobertJ.Evans,Ph.D.bob.evans@ieee.org13ClockJitter•ClockJitteroccurswhentheclockperiodvariesfromoneperiodtothenextClockDriverlUsuallycausedbyPLLinstabilityintheclockdriver•Jitterincreases/decreasestheclockperiod,decreasingtheeffectiveclockcycleCycle1Cycle2CourtesyofCADENCERobertJ.Evans,Ph.D.bob.evans@ieee.org14InsertCADENCEFallingEdgeVariousTimingMeasurementsCourtesyofCADENCERobertJ.Evans,Ph.D.bob.evans@ieee.org15WaveformatReceiverInputWaveformatDriverOutputEndingSteady-StateValueVih-minVmeasOutputBufferThresholdVil-maxStartingSteady-StateValueMax.InterconnectDelayOutputBufferDelayMin.InterconnectDelay(FirstSwitchDelay,MinFlightTime)FinalSettleDelay(MaxFlightTime)RobertJ.Evans,Ph.D.bob.evans@ieee.orgSettlingDelayRisingEdgeTimings16WaveformatDriverOutputWaveformatReceiverInputStartingSteady-StateValueVih-minVmeasOutputBufferThresholdVil-maxEndingSteady-StateValueSettlingDelayMax.InterconnectDelayOutputBufferDelayMin.InterconnectDelay(FirstSwitchDelay,MinFlightTime)FinalSettleDelay(MaxFlightTime)RobertJ.Evans,Ph.D.bob.evans@ieee.orgFallingEdgeTimings17StandardBufferDelay-Thetimeittakestherising(falling)edgeofthedrivertoreachtheoutputbufferthresholdlevelVmeas.Usuallyfoundonspec.sheets.Alsocalled:•StandardDelay•TCO(TimeClocktoOutput)•OutputBufferDelayCload10pFVmeasOutputBufferDelayOutputBufferThresholdRobertJ.Evans,Ph.D.bob.evans@ieee.org18StandardBufferDelayBeCareful!Cload!!CircuitLoadsarenotalwaysequaltotheStandardLoadThetimingmustbe“De-Rated”toaccountforthedifferencesinthedriverloadingfromthereferenceload..•LessLoadingonthedriverwillproducefasterdriverrisetimes,•GreaterLoadingonthedriverwillproduceslowerdriverrisetimes.Somesimulationtoolsgivethe“de-rated”timings,somegivetimingsfromthestandardloads.RobertJ.Evans,Ph.D.bob.evans@ieee.org19VariousTimingMeasurementsCourtesyofCADENCERobertJ.Evans,Ph.D.bob.evans@ieee.org20Non-MonotonicEdges(a.k.a.Knees,Porches)GroundReferenceRobertJ.Evans,Ph.D.bob.evans@ieee.org21NoisySignal,Non-MonotonicEdgesNoisyHighLevelNon-MonotonicViolationHighThresholdLowThresholdNoisyLowLevelCourtesyofIntelCorp.RobertJ.Evans,Ph.D.bob.evans@ieee.org22NoisySignal,Non-MonotonicEdgesCourtesyofCADENCERobertJ.Evans,Ph.D.bob.evans@ieee.org23AcceptableSignalQuality?HighThresholdLowThresholdYes,NotIdeal,butOKKneeisoutsidetransitionregionofthereceiverRobertJ.Evans,Ph.D.bob.evans@ieee.org24ExcessiveSignalRingingVccSignalRingingGnd•HFNoiseSource•WastesPowerRobertJ.Evans,Ph.D.bob.evans@ieee.org25GlitchesintheSignalCourtesyofIntelCorp.RobertJ.Evans,Ph.D.bob.evans@ieee.org26OurSignalParameterDefinitions/StandardsFrequency/Period:SignalRising(Falling)Mid-pointtoNextRising(Falling)Mid-pointHighTime:LowTime:DutyCycle:TransitionRegion:Overshoot:Ringback:SignalTimeAboveVih-minSignalTimeBelowVil-maxTimeAboveMid-Reference/TotalTimePeriodAreaBetweenVil-maxandVih-minInitialtransientresponsewhichexceedsthesteadystateresponse,Expressedinabsolutevoltagelevels(NOTrelativevoltages)Areboundofthesignalafteranovershoothasoccurred,Expressedinabsolutevoltagelevels(NOTrelativevoltages)NoiseMarginHigh:NoiseMarginLow:RingbackVoltage-Vih-minVil-max-RingbackVoltageRobertJ.Evans,Ph.D.bob.evans@ieee.org27OurSignalParameterDefinitions/StandardsRise/FallTimes:Thetimeittakesforasignaltotransitionfrom10%to90%ofitsfinalsettlinglevel.(Somegroupsuse20%to80%)TimingSkew:Thetimedifferencebetweensignalsinagrouparrivingattheirdestinations.TimeofFlight/PropagationDelay:MeasuredfromthesignalatthedrivercrossingVmeastothesignalatthereceivercrossingVil-maxorVih-min.SettlingTime:ThetimefromthesignalatthereceivercrossingVih-min,tothefinalcrossingofthereceiversignaloutofthetransitionregion(aboveVih-min)Jitter:Themaximumvariationofaclockperiodat(mid-level)overalongperiodoftime(i.e.1000cycles)Arisingorfallingwaveformedgeisnon-monotonic,iftheedgebeginstomakeatransitionbutreversesdirectiontwoormoretimesbeforecompletingtransition).Non-Monotonicity:RobertJ.Evans,Ph.D.bob.evans@ieee.org28Vih-minVil-maxDutyCycle:RobertJ.Evans,Ph.D.HighTime:bob.evans@ieee.orgLowTime:RiseTime(10-90):29Vih-minVil-maxOvershoot(High):RobertJ.Evans,Ph.D.NM(High):Ringback(High):bob.evans@ieee.orgOvershoot(Low):NM(Low):Ringback(Low):30Vih-minVmeasVil-maxOutputBufferDelay:RobertJ.Evans,Ph.D.FirstSwitchTime:bob.evans@ieee.orgFinalSettleTime:31