LM2407

LM2407 TI1 | Alldatasheet

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www.ti.com SNOS021C –AUGUST 1999–REVISED APRIL 2013 LM2407MonolithicTriple7.5nSCRTDriver Check forSamples: LM2407 1FEATURES DESCRIPTION The LM2407 isan integratedhighvoltageCRT driver 2• Low Power Dissipation circuitdesignedforuse incolormonitorapplications.• WellMatched withLM1279 Video Preamp The IC containsthreehigh inputimpedance, wide

• 0V to5V InputRange band amplifierswhich directlydrive the RGB cathodes of a CRT. Each channel has itsgain• Stablewith0 pF–20 pF CapacitiveLoads and internallyset to −14 and can driveCRT capacitiveInductivePeaking Networks loads as well as resistiveloads presentin other• Convenient TO-220 Staggered Lead Package applications,limitedonly by the package'spowerStyle dissipation.
• Standard LM240X FamilyPinoutwhich is The IC ispackaged inan industrystandard11-leadDesigned forEasy PCB Layout TO-220 molded plasticpower package. See THERMAL CONSIDERATIONS on page 7.APPLICATIONS
• 1024 x 768 DisplaysUp To 85 Hz Refresh
• PixelClock FrequenciesUp To 100 MHz
• MonitorsUsing Video Blanking Schematic and Connection Diagrams Note:Tab isatGND Figure1.SimplifiedSchematic Diagram Figure2.Top View (One Channel) Pleasebe aware thatan importantnoticeconcerningavailability,standardwarranty,and use incriticalapplicationsof Texas Instrumentssemiconductorproductsand disclaimerstheretoappearsattheend ofthisdatasheet. 2Alltrademarksarethepropertyoftheirrespectiveowners. PRODUCTION DATA informationiscurrentas ofpublicationdate. Copyright© 1999–2013,Texas InstrumentsIncorporatedProductsconform to specificationsper the terms of the Texas Instrumentsstandardwarranty.Productionprocessingdoes not necessarilyincludetestingofallparameters.

SNOS021C –AUGUST 1999–REVISED APRIL 2013 www.ti.com These deviceshave limitedbuilt-inESD protection.The leadsshouldbe shortedtogetherorthedeviceplacedinconductivefoam duringstorageorhandlingtopreventelectrostaticdamage totheMOS gates. ABSOLUTE MAXIMUM RATINGS (1)(2)(3) SupplyVoltage,(VCC ) +90V BiasVoltage,(VBB ) +16V InputVoltage,(VIN) −0.5VtoVBIAS +0.5V StorageTemperatureRange, (TSTG ) −65°C to+150°C Lead Temperature Soldering,<10 sec 300°C ESD Tolerance Human Body Model 2 kV Machine Model 300V (1) AbsoluteMaximum Ratingsindicatelimitsbeyond whichdamage tothedevicemay occur. (2) Allvoltagesaremeasured withrespecttoGND, unlessotherwisespecified. (3) IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexas InstrumentsSalesOffice/Distributorsforavailabilityand specifications. OPERATING RANGE (1) VCC +60V to+85V VBB +8V to+15V VIN +0V to+5V VOUT +15V to+75V Case Temperature −20°C to+100°C Do notoperatethepartwithouta heatsink. (1) Operatingratingsindicateconditionsforwhichthedeviceisfunctional,butdo notensurespecificperformancelimits.Forensured specificationsand testconditions,see theELECTRICAL CHARACTERISTICS section.The ensuredspecificationsapplyonlyforthetest conditionslisted.Some performancecharacteristicsmay change when thedeviceisnotoperatedunderthelistedtestconditions.

ELECTRICAL CHARACTERISTICS

(See Figure3 forTestCircuit) Unlessotherwisenoted:VCC = +80V, VBB = +12V, VIN = +2.7VDC ,C L = 8 pF,Output= 40 VPP at1 MHz, TC = 50°C. LM2407 Symbol Parameter Condition Units Min Typical Max ICC SupplyCurrent Per Channel,No OutputLoad 11.5 mA IBB BiasCurrent AllThreeChannels 11 mA VOUT DC OutputVoltage No AC InputSignal,VIN = 1.2V 62 65 68 VDC AV DC VoltageGain No AC InputSignal −13.3 −13.9 −14.5 ΔAV Gain Matching No AC InputSignal(1) 1.0 dB LE LinearityError No AC InputSignal(1)(2) 8 % tR RiseTime(3) 10% to90% 7.5 nS tF FallTime(3) 90% to10% 7.5 nS OS Overshoot RisingEdge 8 % FallingEdge 2 (1) CalculatedvaluefromVoltageGain teston each channel. (2) LinearityErroristhevariationindc gainfromVIN = 1.0VtoVIN = 4.5V. (3) Inputfromsignalgenerator:tr,tf< 1 nS.

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www.ti.com SNOS021C –AUGUST 1999–REVISED APRIL 2013 AC TEST CIRCUIT Note:8 pF loadincludesparasiticcapacitance. Figure3. TestCircuit(One Channel) Figure3 shows a typicaltestcircuitforevaluationoftheLM2407. Thiscircuitisdesignedtoallowtestingofthe LM2407 ina 50Ω environmentwithoutthe use of an expensiveFET probe.The 4950Ω resistorat the output formsa 100:1voltagedividerwhen connectedtoa 50Ω load. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 3 ProductFolderLinks:LM2407

SNOS021C –AUGUST 1999–REVISED APRIL 2013 www.ti.com VOUT vs VIN Speed vs Temp. Figure4. Figure5. LM2407 Pulse Response Power Dissipationvs Frequency Figure6. Figure7. Speed vs Offset Speed vs Load Capacitance Figure8. Figure9.

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www.ti.com SNOS021C –AUGUST 1999–REVISED APRIL 2013 THEORY OF OPERATION The LM2407 is a high voltagemonolithicthree channel CRT driversuitablefor high resolutiondisplay applications.The LM2407 operatesusing80V and 12V power supplies.The partishoused in the industry standard11-leadTO-220 molded plasticpower package. The circuitdiagramoftheLM2407 isshown inFigure1.A PNP emitterfollower,Q5, providesinputbuffering.Q1 and Q2 forma fixedgaincascode amplifierwithresistorsR1 and R2 settingthegainat-14.EmitterfollowersQ3 and Q4 isolatethehighoutputimpedance ofthecascode stagefromthecapacitanceoftheCRT cathodewhich decreasesthe sensitivityof the deviceto loadcapacitance.Q6 providesbiasingto the outputemitterfollower stagetoreducecrossoverdistortionatlowsignallevels. Figure3 shows a typicaltestcircuitforevaluationoftheLM2407. Thiscircuitisdesignedtoallowtestingofthe LM2407 ina 50Ω environmentwithouttheuse ofan expensiveFET probe.Inthistestcircuit,two low inductance resistorsinseriestotaling4.95 kΩ form a 100:1 wideband,low capacitanceprobe when connectedto a 50Ω coaxialcableand a 50Ω load(suchas a 50Ω oscilloscopeinput).The inputsignalfrom the generatorisac coupledtothebase ofQ1. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 5 ProductFolderLinks:LM2407

SNOS021C –AUGUST 1999–REVISED APRIL 2013 www.ti.com APPLICATION HINTS INTRODUCTION Texas Instruments(TI)iscommittedtoprovideapplicationinformationthatassistsourcustomersinobtainingthe best performancepossiblefrom our products.The followinginformationisprovidedin orderto supportthis commitment.The readershouldbe aware thattheoptimizationofperformancewas done usinga specificprinted circuitboard designedatTI.Variationsinperformancecan be realizeddue tophysicalchanges intheprinted circuitboard and theapplication.Therefore,thedesignershouldknow thatcomponent valuechanges may be requiredinordertooptimizeperformanceina givenapplication.The valuesshown inthisdocument can be used as a startingpointforevaluationpurposes.When workingwithhighbandwidthcircuits,good layoutpracticesare alsocriticaltoachievingmaximum performance. IMPORTANT INFORMATION The LM2407 performanceistargetedforthe XGA resolutionmarket (1024 x 768, 85 Hz refresh).Itisnot designedto be a directreplacementforthe LM2405 or LM2406. The applicationcircuitsrequiredto optimize performanceand toprotectagainstdamage fromCRT arcoveraredifferentforeach part.The applicationsection inthisdocument providesinformationfortheLM2407. PleaserefertotheLM2405 and LM2406 datasheetsfor specificapplicationinformationon each ofthosedevices. POWER SUPPLY BYPASS Since the LM2407 is a high bandwidth amplifier,proper power supply bypassingis criticalforoptimum performance.Improperpower supplybypassingcan resultinlargeovershoot,ringingand oscillation.A 0.01µF capacitorshouldbe connectedfromthesupplypin,VCC ,toground,as closetothesupplyand groundpinsas is practical.Additionally,a 10 µF to 100 µF electrolyticcapacitorshouldbe connectedfrom the supplypin to ground.The electrolyticcapacitorshouldalsobe placedreasonablyclosetotheLM2407's supplyand ground pins.A 0.1µF capacitorshouldbe connectedfrom thebiaspin,VBB ,toground,as closeas ispracticaltothe part. ARC PROTECTION During normal CRT operation,internalarcingmay occasionallyoccur.Spark gaps, in the range of 200V, connectedfrom theCRT cathodestoCRT ground willlimitthemaximum voltage,buttoa valuethatismuch higherthanallowableon theLM2407. Thisfast,highvoltage,highenergypulsecan damage theLM2407 output stage.The applicationcircuitshown inFigure10 isdesignedto helpclamp the voltageat the outputof the LM2407 toa safelevel.The clamp diodesshouldhave a fasttransientresponse,highpeak currentrating,low seriesimpedance and low shunt capacitance.FDH400 or equivalentdiodesare recommended. D1 and D2 shouldhave short,low impedance connectionsto VCC and ground respectively.The cathodeof D1 shouldbe locatedveryclosetoa separatelydecoupledbypass capacitor(C3 inFigure10).The groundconnectionofthe diodeand thedecouplingcapacitorshouldbe veryclosetotheLM2407 ground.Thiswillsignificantlyreducethe highfrequencyvoltagetransientsthattheLM2407 would be subjectedtoduringan arcovercondition.Resistor R2 limitsthearcovercurrentthatisseen by thediodeswhileR1 limitsthecurrentintotheLM2407 as wellas the voltagestressattheoutputsofthedevice.R2 shouldbe a 1/2W solidcarbontyperesistor.R1 can be a 1/4W metalorcarbonfilmtyperesistor.InductorL1 iscriticaltoreducetheinitialhighfrequencyvoltagelevelsthatthe LM2407 would be subjectedto.HavinglargevalueresistorsforR1 and R2 would be desirable,butthishas the effectof increasingriseand falltimes.The inductorwillnot onlyhelpprotectthe devicebut itwillalsohelp optimizeriseand falltimesas wellas minimizeEMI. For properarcprotection,itisimportanttonotomitany of thearcprotectioncomponents shown inFigure10.

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www.ti.com SNOS021C –AUGUST 1999–REVISED APRIL 2013 Figure10. One Channel oftheLM2407 withtheRecommended Arc ProtectionCircuit OPTIMIZING TRANSIENT RESPONSE Referringto Figure10, thereare threecomponents (R1, R2 and L1) thatcan be adjustedto optimizethe transientresponseoftheapplicationcircuit.IncreasingthevaluesofR1 and R2 willslowthecircuitdown while decreasingovershoot.IncreasingthevalueofL1 willspeed up thecircuitas wellas increaseovershoot.Itisvery importantto use inductorswithvery high self-resonantfrequencies,preferablyabove 300 MHz. Ferritecore inductorsfromJ.W.MillerMagnetics(part# 78FR56M) were used foroptimizingtheperformanceofthedevicein theTIapplicationboard.The valuesshown inFigure10 can be used as a good startingpointfortheevaluation oftheLM2407. The TIdemo boardalsohas a positionopen toadd a resistorinparallelwithL1.Thisresistorcan be used tohelpcontrolovershoot.UsingvariableresistorsforR1 and theparallelresistorisa greatway tohelp dialin the valuesneeded foroptimum performancein a given application.Once the optimum valuesare determinedthevariableresistorscan be replacedwithfixedvalues. EffectofLoad Capacitance Figure9 shows the effectof increasedloadcapacitanceon the speed of the device.Thisdemonstratesthe importanceofknowing theloadcapacitanceintheapplication.The previoussectiondiscussedhow tooptimize thetransientresponseintheapplicationwiththeuse ofa seriesinductor. EffectofOffset Figure8 shows thevariationinriseand falltimeswhen theoutputoffsetofthedeviceisvariedfrom40 VDC to50 VDC .The risetimeshows a maximum variationrelativetothecenterdatapoint(45 VDC ) isabout20%. The fall timeshows a variationofabout5% relativetothecenterdatapoint. THERMAL CONSIDERATIONS Figure5 shows the performanceof the LM2407 in the testcircuitshown in Figure3 as a functionof case temperature.The figureshows thatthe risetimeof the LM2407 decreasesby approximately5% as the case temperatureincreasesfrom50°C to100°C. Thiscorrespondstoa speed degradationof1% forevery10°C rise incase temperature.Thereisa negligiblechange infalltimeversustemperatureinthetestcircuit. Figure7 shows thetotalpower dissipationoftheLM2407 vs.Frequencywhen allthreechannelsofthedevice are drivingan 8 pF loadwitha 40Vp-p signal.The graph assumes a 72% activetime(deviceoperatingatthe specifiedfrequency)whichistypicalina monitorapplication.The other28% ofthetimethedeviceisassumed to be sittingattheblacklevel(65V inthiscase).Thisgraphgivesthedesignertheinformationneeded todetermine theheatsinkrequirementforhisapplication.The designershouldnotethatiftheloadcapacitanceisincreased theAC component ofthetotalpower dissipationwillalsoincrease. The LM2407 case temperaturemust be maintainedbelow 100°C. Ifthemaximum expectedambienttemperature is50°C and the maximum power dissipationis6.2W, then a maximum heat sinkthermalresistancecan be calculated: (1) Thisexample assumes a capacitiveloadof8 pF and no resistiveload. Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 7 ProductFolderLinks:LM2407

SNOS021C –AUGUST 1999–REVISED APRIL 2013 www.ti.com TYPICAL APPLICATION A typicalapplicationoftheLM2407 isshown inFigure11.Used inconjunctionwithan LM1279, a completevideo channelfrom monitorinputto CRT cathodecan be achieved.Performanceisidealfor1024 x 768 resolution displayswithpixelclockfrequenciesup to100 MHz. Figure11 istheschematicfortheTI demonstrationboard thatcan be used toevaluatetheLM1279/2407 combinationina monitor. PC Board Layout Considerations For optimum performance,an adequateground plane,isolationbetween channels,good supplybypassingand minimizingunwanted feedbackare necessary.Also,thelengthofthesignaltracesfrom thepreamplifiertothe LM2407 and fromtheLM2407 totheCRT cathodeshouldbe as shortas possible.The followingreferencesare recommended: Ott,Henry W., “NoiseReductionTechniquesinElectronicSystems”2nd Edition,John Wiley& Sons,New York, 1988. “Guide toCRT VideoDesign”,Texas InstrumentsApplicationNote 861. “VideoAmplifierDesignforComputer Monitors”,Texas InstrumentsApplicationNote 1013. Pease,RobertA.,“TroubleshootingAnalogCircuits”,Butterworth-Heinemann,1991. Because of itshighsmallsignalbandwidth,the partmay oscillateina monitoriffeedbackoccursaround the videochannelthroughthe chassiswiring.To preventthis,leadsto the videoamplifierinputcircuitshouldbe shielded,and inputcircuitwiringshouldbe spaced as faras possiblefromoutputcircuitwiring. TIDemonstrationBoard Figure12 shows routingand component placementon theTILM1279/2407 demonstrationboard.The schematic oftheboardisshown inFigure11.Thisboardprovidesa good example ofa layoutthatcan be used as a guide forfuturelayouts.Note thelocationofthefollowingcomponents:

• C55 — VCC bypasscapacitor,locatedveryclosetopin6 and groundpins
• C43, C44 — VBB bypasscapacitors,locatedclosetopin10 and ground
• C53 –C55 — VCC bypasscapacitors,nearLM2407 and VCC clamp diodes.Veryimportantforarcprotection The routingof the LM2407 outputsto the CRT isverycriticalto achievingoptimum performance.Figure13 shows the routingand component placementfrom pin 1 of the LM2407 to the blue cathode.Note thatthe components areplacedso thattheyalmostlineup fromtheoutputpinoftheLM2407 tothebluecathodepinof theCRT connector.Thisisdone tominimizethelengthofthevideopathbetween thesetwo components.Note alsothatD14, D15, R29 and D13 areplacedtominimizethesizeofthevideonodes thattheyareattachedto. Thisminimizesparasiticcapacitanceinthe videopath and alsoenhances the effectivenessof the protection diodes.The anode ofprotectiondiodeD14 isconnecteddirectlytoa sectionofthethegroundplanethathas a shortand directpath to the LM2407 ground pins.The cathode of D15 is connected to VCC very closeto decouplingcapacitorC55 (seeFigure13) which isconnectedtothesame sectionoftheground planeas D15. The diodeplacementand routingisveryimportantforminimizingthevoltagestresson theLM2407 duringan arc overevent.Lastly,noticethatS1 isplacedveryclosetothebluecathodeand istieddirectlytoCRT ground.

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www.ti.com SNOS021C –AUGUST 1999–REVISED APRIL 2013 Figure11. LM1279/240X DemonstrationBoard Schematic Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 9 ProductFolderLinks:LM2407

SNOS021C –AUGUST 1999–REVISED APRIL 2013 www.ti.com Figure12. LM1279/240X Demo Board Layout

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www.ti.com SNOS021C –AUGUST 1999–REVISED APRIL 2013 Figure13. Trace Routing and Component Placement forBlue Channel Output Copyright© 1999–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 11 ProductFolderLinks:LM2407

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REVISION HISTORY

Changes from RevisionB (April2013)toRevisionC Page

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