ESD Protection Design Seminr.ppt

ESDProtectionDesignSeminarJimSutherlandSeniorApplicationsEngineer,Outline,WhatisESD?Whatdamagecanitcause?Whyistheproblemgrowing?Whataretheissuesforthedesigner?Howcanwemeasureit?HowcanweprotectequipmentfromESD?,WhatIsESD?,ESD=ElectroStaticDischargeGenerationTriboelectric(frictioncausesaccumulationofcharge)Induction(fieldinducescharge)DischargeDielectric(air)breakdownElectricfieldincreaseswhenchargedbodiesapproacheachotherCurrentflowintocircuitry,ESDDamageofICs,PermanentOxidebreakdown,shorts,opens,latch-upTemporaryLatch-up,groundbounceLatentDegradationfromanESDevent,ESDproblemisgrowing,Circuits/SystemsOld-RobustICsmanycomponents;largeboardareaSparkgapLowcost;lowstability;largeboardareaDiscreteZenerdiodesHighcapacitance,manycomponents;largeboardareaDiscretePNdiodesLowcapacitance;manycomponents;largeboardareaIntegratedPNdiodes,IntegratedDiodeNetworks,SuperiordownstreamESDprotectionHighspeedresponseESDcurrentsteeredtoGNDorVCCMinimumSignalDegradation(LowC)Minimalboardspace,weightLowassembly/manufacturingcostsMinimalDesign-InTimeLong-termreliability,ChoosinganESDDiodeNetwork,Howmanylinesareneeded?Howmuchcapacitance?(e.g.5pF)WhatistheHBMrating?(e.g.15kV)Whatisthedownstreamclampvoltage?(e.g.13V15kVHBMpulse)Whatisthecontactdischargerating?(e.g.8kV)Whatistheairdischargerating?(e.g.15kV)Whatpackage?(e.g.24-pinQSOP),ESDDiodeNetworkPlacement,TheNeedtoKeepESDDiodes,DownstreamofLineInductances,AlsoputprotectiondiodesatmostlikelyESDentrypoint-theconnector,DesigningforMinimalPowerRailInductance,AddBypassCapacitor,PlaceCeramicbypasscapacitor(0.10.2uF)ascloseaspossibletoESDdiodenetworkpowerrailtoshuntESDcurrenttobothpowerrailsMaybeaddZenerinparallelwithcapacitortominimizeparasiticinductanceofbypasscapacitor,Protected,Device,Gnd,Vcc,C,UsingaSeriesResistortoMinimizeDownstreamCurrent,Canbeconsideredforlatch-upsensitiveapplicationsGuaranteedclampingvoltagelimitscurrentdownstream(I=V/R)OnlyforinputswithhighZOnlyforoutputdriverswithlowZwatchoutforfilteringofsignal,Power-downIssues,DiodeprotectedsystemsthatarepowereddowncandraincurrentfromanactivehighinputthroughthediodetoVCCThiscandrainbatteriesand/ordamagedevicesonthesamelineToavoidthis,isolateVCCfromthebypasscapacitorwithablockingdiodeOnediodesolution,ComponentandSystemSpecifications,ThereisnosimpleformulatotranslatesystemspecificationsintocomponentspecificationsIEC1000-4-2SpecificationismoreseverethanHBMLinecapacitanceandinductanceshapetheESDpulse,reducingitspeakvaluePoordeviceplacementcandegradeperformanceIftherearemultipledevicesonaline,decidewhichtoprotectTherelationshipbetweendownstreamclampvoltageanddownstreamprotectionisnotexact,ValidatingtheDesign,Definethepracticallimitsoffunctionalfailure(e.g.Dataintegrity,recoverytime)TestonlyatthoseplacessubjecttotouchduringnormaloperationUseContactESDischargestocouplingplanes&conductivesurfaces,I/Opins,flexpads,andpowerpinsUseAirESDischargestoinsulatingsurfaces,openingsatedgesofkeys,flexcables,ventareas,seams,slots,apertures,TotalSolutionCost,ESDfailureisaquestionofstatisticsOnecannot