DS0026H资料

DS0026DualHigh-SpeedMOSDriverFebruary2002

DS0026

DualHigh-SpeedMOSDriver

GeneralDescription

DS0026isalowcostmonolithichighspeedtwophaseMOSclockdriverandinterfacecircuit.Uniquecircuitdesignpro-videsbothveryhighspeedoperationandtheabilitytodrivelargecapacitiveloads.ThedeviceacceptsstandardTTLoutputsandconvertsthemtoMOSlogiclevels.Thedevicemaybedrivenfromstandard/74seriesandS/74Sseriesgatesandflip-flopsorfromdriverssuchastheDS8830orDM7440.TheDS0026isintendedforapplica-tionsinwhichtheoutputpulsewidthislogicallycontrolled;i.e.,theoutputpulsewidthisequaltotheinputpulsewidth.TheDS0026isdesignedtofulfillawidevarietyofMOSinterfacerequirements.InformationonthecorrectusageoftheDS0026intheseaswellasothersystemsisincludedintheapplicationnoteAN-76.

Features

nnnnn

Fastriseandfalltimes—20ns1000pFloadHighoutputswing—20V

Highoutputcurrentdrive—±1.5ampsTTLcompatibleinputs

Highreprate—5to10MHzdependingonpowerdissipation

nLowpowerconsumptioninMOS“0”state—2mWnDrivesto0.4VofGNDforRAMaddressdrive

ConnectionDiagram(TopView)

Dual-In-LinePackage

00585302

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DS0026AbsoluteMaximumRatings

(Note1)

OperatingRatings

(V+)−(V−)DifferentialVoltageMaximumPowerDissipationatTA=25˚C(Note7)N08EθJAN08EθJCM08AθJAMUA08AθJAOperatingTemperatureRange,TA10Vto20V1168mW107˚C/W37˚C/W180˚C/W220˚C/W0˚Cto+70˚C

IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.(V+)−(V−)DifferentialVoltageInputCurrent

InputVoltage(VIN)−(V−)PeakOutputCurrentStorageTemperatureRangeLeadTemperature(Soldering,10sec.)

22V100mA5.5V1.5A

−65˚Cto+150˚C

300˚C

OrderingInformation

OrderNumberDS0026CNDS0026CMADS0026CMM

PackageType

M-DIPSOICMSOP

NSPackageNumber

N08EM08AMUA08A

ElectricalCharacteristics(Notes2,3,4)

SymbolVIHIIHVILIILVOLVOHICC(ON)ICC(OFF)Parameter

Logic“1”InputVoltageLogic“1”InputCurrentLogic“0”InputVoltageLogic“0”InputCurrentLogic“1”OutputVoltageLogic“0”OutputVoltage“ON”SupplyCurrent(onesideon)“OFF”SupplyCurrent

V=0VVIN−V=2.4VV=0VVIN−V=0V

VIN−V=2.4V,IOL=1mAVIN−V−=0.4V,VSS≥V++1.0VIOH=−1mA

V+−V−=20V,VIN−V−=2.4VV+−V−=20V,VIN−V−=0V

V+−1.0

−−−−−ConditionsMin2

Typ1.5100.6−3V+0.7V+−0.83010

−Max150.4−10V+1.0

−UnitsVmAVµAVV

40100

mAµA

SwitchingCharacteristics

(TA=25˚C)(Notes5,6)SymboltONtOFFtrParameterTurn-OnDelayTurn-OffDelayRiseTime

Conditions

Min5

Typ7.5111213

CL=500pFCL=1000pFCL=500pFCL=1000pFCL=500pFCL=1000pFCL=500pFCL=1000pF

1520303612172831

18305016253015Max12

Unitsnsnsnsnsnsnsnsnsnsnsnsns

(Figure1)(Figure2)(Figure1)(Figure2)(Figure1),(Note5)(Figure2),(Note5)

tfFallTime

(Figure1),(Note5)(Figure2),(Note5)

Note1:“AbsoluteMaximumRatings”arethosevaluesbeyondwhichthesafetyofthedevicecannotbeguaranteed.Exceptfor“OperatingTemperatureRange”theyarenotmeanttoimplythatthedevicesshouldbeoperatedattheselimits.Thetableof“ElectricalCharacteristicsprovidesconditionsforactualdeviceoperation.Note2:ThesespecificationsapplyforV+−V−=10Vto20V,CL=1000pF,overthetemperaturerangeof0˚Cto+70˚CfortheDS0026CN.

Note3:Allcurrentsintodevicepinsshownaspositive,outofdevicepinsasnegative,allvoltagesreferencedtogroundunlessotherwisenoted.Allvaluesshownasmaxorminonabsolutevaluebasis.

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DS0026SwitchingCharacteristics

Note4:AlltypicalvaluesforTA=25˚C.

(Continued)

Note5:RiseandfalltimearegivenforMOSlogiclevels;i.e.,risetimeistransitionfromlogic“0”tologic“1”whichisvoltagefall.

Note6:Thehighcurrenttransient(ashighas1.5A)throughtheresistanceoftheinternalinterconnectingV−leadduringtheoutputtransitionfromthehighstatetothelowstatecanappearasnegativefeedbacktotheinput.IftheexternalinterconnectingleadfromthedrivingcircuittoV−iselectricallylong,orhassignificantdcresistance,itcansubtractfromtheswitchingresponse.Note7:DerateN08Epackage9.3mW/˚CforTAabove25˚C.

TypicalVBBConnection

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TypicalPerformanceCharacteristics

InputCurrentvsInputVoltage

SupplyCurrentvsTemperature

Turn-OnandTurn-OffDelay

vsTemperature

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00585322

00585324

RiseTimevsLoad

CapacitanceFallTimevsLoadCapacitance

0058532500585326

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DS0026TypicalPerformanceCharacteristics

RecommendedInputCoding

Capacitance

(Continued)

DCPower(PDC)vs

DutyCycle

00585328

00585327

SchematicDiagram

1/2DS0026

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DS0026ACTestCircuitsandSwitchingTimeWaveforms

00585313

00585312

FIGURE1.

00585315

00585314

FIGURE2.

TypicalApplications

ACCoupledMOSClockDriver

00585317

00585316

DCCoupledRAMMemoryAddressorPrecharge

Driver(PositiveSupplyOnly)

ApplicationHints

DRIVINGTHEMM5262WITHTHEDS0026CLOCKDRIVER

TheclocksignalsfortheMM5262havethreerequirementswhichhavethepotentialofgeneratingproblemsfortheuser.Theserequirements,highspeed,largevoltageswingandlargecapacitiveloads,combinetoprovideampleopportunityforinductiveringingonclocklines,couplingclocksignalstootherclocksand/orinputsandoutputsandgeneratingnoiseonthepowersupplies.Alloftheseproblemshavethepo-tentialofcausingthememorysystemtomalfunction.Rec-ognizingthesourceandpotentialoftheseproblemsearlyinthedesignofamemorysystemisthemostcriticalstep.Theobjecthereistopointoutthesourceoftheseproblemsandgiveaquantitativefeelfortheirmagnitude.

5

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DS0026ApplicationHints

(Continued)

Lineringingcomesfromthefactthatatahighenoughfrequencyanylinemustbeconsideredasatransmissionlinewithdistributedinductanceandcapacitance.Toseehowmuchringingcanbetoleratedwemustexaminetheclockvoltagespecification.Figure3showstheclockspecification,indiagramform,withidealizedringingsketchedin.TheringingoftheclockabouttheVSSlevelisparticularlycritical.IftheVSS−1VOHisnotmaintained,atalltimes,theinformationstoredinthememorycouldbealtered.ReferringtoFigure1,ifthethresholdvoltageofatransistorwere−1.3V,theclockgoingtoVSS−1wouldmeanthatallthedevices,whosegatesaretiedtothatclock,wouldbeonly300mVfromturningon.TheinternalcircuitryneedsthisnoisemarginandfromthefunctionaldescriptionoftheRAMitiseasytoseethatturningaclockonatthewrongtimecanhavedisastrousresults.

aremoreexpensivethantwosidedboards.Theusermustmakethedecisionastothenecessityofmultilayerboards.Sufficeittosayhere,thatreliablememoryboardscanbedesignedusingtwosidedprintedcircuitboards.

00585318

FIGURE3.ClockWaveform

Controllingtheclockringingisparticularlydifficultbecauseoftherelativemagnitudeoftheallowableringing,comparedtomagnitudeofthetransition.Inthiscaseitis1Voutof20Voronly5%.Ringingcanbecontrolledbydampingtheclockdriverandminimizingthelineinductance.

Dampingtheclockdriverbyplacingaresistanceinserieswithitsoutputiseffective,butthereisalimitsinceitalsoslowsdowntheriseandfalltimeoftheclocksignal.Becausethetypicalclockdrivercanbemuchfasterthantheworstcasedriver,thedampingresistorservestheusefulfunctionoflimitingtheminimumriseandfalltime.Thisisveryimpor-tantbecausethefastertheriseandfalltimes,theworsetheringingproblembecomes.Thesizeofthedampingresistorvariesbecauseitisdependentonthedetailsoftheactualapplication.Itmustbedeterminedempirically.Inpracticearesistanceof10Ωto20Ωisusuallyoptimum.

Limitingtheinductanceoftheclocklinescanbeaccom-plishedbyminimizingtheirlengthandbylayingoutthelinessuchthatthereturncurrentiscloselycoupledtotheclocklines.Whenminimizingthelengthofclocklinesitisimpor-tanttominimizethedistancefromtheclockdriveroutputtothefurthestpointbeingdriven.Becauseofthis,memoryboardsareusuallydesignedwithclockdriversinthecenterofthememoryarray,ratherthanononeside,reducingthemaximumdistancebyafactorof2.

Usingmultilayerprintedcircuitboardswithclocklinessand-wichedbetweentheVDDandVSSpowerplainsminimizestheinductanceoftheclocklines.Italsoservesthefunctionofpreventingtheclocksfromcouplingnoiseintoinputandoutputlines.Unfortunatelymultilayerprintedcircuitboards

00585319

FIGURE4.ClockWaveforms(VoltageandCurrent)Becauseoftheamountofcurrentthattheclockdrivermustsupplytoitscapacitiveload,thedistributionofpowertotheclockdrivermustbeconsidered.Figure4givestheidealizedvoltageandcurrentwaveformsforaclockdriverdrivinga1000pFcapacitorwith20nsriseandfalltime.

Ascanbeseenthecurrentissignificant.ThiscurrentflowsintheVDDandVSSpowerlines.Anysignificantinductanceinthelineswillproducelargevoltagetransientsonthepowersupplies.Abypasscapacitor,ascloseaspossibletotheclockdriver,ishelpfulinminimizingthisproblem.Thisby-passismosteffectivewhenconnectedbetweentheVSSandVDDsupplies.Thesizeofthebypasscapacitordependsontheamountofcapacitancebeingdriven.Usingalowinduc-tancecapacitor,suchasaceramicorsilvermica,ismosteffective.AnotherhelpfultechniqueistoruntheVDDandVSSlines,totheclockdriver,adjacenttoeachother.Thistendstoreducethelinesinductanceandthereforethemag-nitudeofthevoltagetransients.

Whilediscussingtheclockdriver,itshouldbepointedoutthattheDS0026isarelativelylowinputimpedancedevice.Itispossibletocouplecurrentnoiseintotheinputwithoutseeingasignificantvoltage.Sincethenoiseisdifficulttodetectwithanoscilloscopeitisoftenoverlooked.

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DS0026ApplicationHints

(Continued)

Lastly,theclocklinesmustbeconsideredasnoisegenera-tors.Figure5showsaclockcoupledthroughaparasiticcouplingcapacitor,CC,toeightdatainputlinesbeingdrivenbya7404.Aparasiticlumpedlineinductance,L,isalsoshown.Letusassume,forthesakeofargument,thatCCis1pFandthattherisetimeoftheclockishighenoughtocompletelyisolatetheclocktransientfromthe7404becauseoftheinductance,L.

Thishasbeenahypotheticalexampletoemphasizethatwith20Vlowrise/falltimetransitions,parasiticelementscannotbeneglected.Inthisexample,1pFofparasiticcapaci-tancecouldcausesystemmalfunction,becausea7404withoutapullupresistorhastypicallyonly0.3Vofnoisemargininthe“1”stateat25˚C.Ofcourseitisstretchingthingstoassumethattheinductance,L,completelyisolatestheclocktransientfromthe7404.However,itdoespointouttheneedtominimizeinductanceininput/outputaswellasclocklines.

Theoutputiscurrent,soitismoremeaningfultoexaminethecurrentthatiscoupledthrougha1pFparasiticcapaci-tance.Thecurrentwouldbe:

00585320

FIGURE5.ClockCoupling

Withaclocktransitionof20VthemagnitudeofthevoltagegeneratedacrossCLis:

Thisexceedsthetotaloutputcurrentswingsoitisobviouslysignificant.

Clockcouplingtoinputsandoutputscanbeminimizedbyusingmultilayerprintedcircuitboards,asmentionedprevi-ously,physicallyisolatingclocklinesand/orrunningclocklinesatrightanglestoinput/outputlines.Allofthesetech-niquestendtominimizeparasiticcouplingcapacitancefromtheclockstothesignalsinquestion.

Inconsideringclockcouplingitisalsoimportanttohaveadetailedknowledgeofthefunctionalcharacteristicsofthedevicebeingused.Asanexample,fortheMM5262,cou-plingnoisefromtheφ2clocktotheaddresslinesisofnoparticularconsequence.Ontheotherhandtheaddressinputswillbesensitivetonoisecoupledfromφ1clock.

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DS0026PhysicalDimensions

inches(millimeters)unlessotherwisenoted

MoldedDual-In-LinePackage(N)

OrderNumberDS0026CNNSPackageNumberN08E

8-LeadSmallOutlineMoldedpackage(M)

NSPackageNumberM08A

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DS0026DualHigh-SpeedMOSDriverPhysicalDimensions

inches(millimeters)unlessotherwisenoted(Continued)

8-LeadMiniSOICPackage(MM)NSPackageNumberMU08A

LIFESUPPORTPOLICY

NATIONAL’SPRODUCTSARENOTAUTHORIZEDFORUSEASCRITICALCOMPONENTSINLIFESUPPORTDEVICESORSYSTEMSWITHOUTTHEEXPRESSWRITTENAPPROVALOFTHEPRESIDENTANDGENERALCOUNSELOFNATIONALSEMICONDUCTORCORPORATION.Asusedherein:1.Lifesupportdevicesorsystemsaredevicesorsystemswhich,(a)areintendedforsurgicalimplantintothebody,or(b)supportorsustainlife,andwhosefailuretoperformwhenproperlyusedinaccordancewithinstructionsforuseprovidedinthelabeling,canbereasonablyexpectedtoresultinasignificantinjurytotheuser.

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2.Acriticalcomponentisanycomponentofalifesupportdeviceorsystemwhosefailuretoperformcanbereasonablyexpectedtocausethefailureofthelifesupportdeviceorsystem,ortoaffectitssafetyoreffectiveness.

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