LM2432

LM2432 TI1 | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 17

Technical content

www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 LM2432220VMonolithicSingleChannel37MHzHDTVCRTDriver Check forSamples: LM2432 1FEATURES DESCRIPTION The LM2432 isa singlechannelhigh voltageCRT 2• 37 MHz Bandwith at110VPP Output Swing drivercircuitdesignedforuse inRear-Projectionand• 0V to4V InputRange Direct-ViewHDTV applications.The IC containsa

• Greaterthan 130VPP Output Swing Capability highinputimpedance,wide band amplifierwhichcan be DC coupledtoa cathodeofa CRT. The amplifier• IK CurrentOutput (Pin5)forIK Feedback has itsgaininternallysetto−53 and can driveCRTSystems capacitiveloadsas wellas resistiveloadspresentin• Stablewith0–20 pF CapacitiveLoads and other applications,limitedonly by the package'sInductivePeaking Networks power dissipation. The IC is packaged in a staggered7-leadTO-220APPLICATIONS molded plasticpower package designedspecifically
• For Rear-Projectionand Direct-ViewDC to meet highvoltagespacingrequirements.See the Coupled CRT ApplicationsUsing up to720p section“POWER DISSIPATION AND HEATSINK and 1080iHDTV Formats CALCULATION ”formore information.
• Compatible withRGB Video Processors with IK Feedback forAutomatic Cathode Calibration PinoutDiagram Schematic Diagram Note:Tab isatGND. Pin6 isnot connected(N/C)internally. Figure1. Top View SimplifiedConnection and PinoutDiagram Figure2. SimplifiedSchematic Diagram These deviceshave limitedbuilt-inESD protection.The leadsshouldbe shortedtogetherorthedeviceplacedinconductivefoam duringstorageorhandlingtopreventelectrostaticdamage totheMOS gates. Pleasebe aware thatan importantnoticeconcerningavailability,standardwarranty,and use incriticalapplicationsof Texas Instrumentssemiconductorproductsand disclaimerstheretoappearsattheend ofthisdatasheet. 2Alltrademarksarethepropertyoftheirrespectiveowners. PRODUCTION DATA informationiscurrentas ofpublicationdate. Copyright© 2005–2013,Texas InstrumentsIncorporatedProductsconform to specificationsper the terms of the Texas Instrumentsstandardwarranty.Productionprocessingdoes not necessarilyincludetestingofallparameters.

SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com ABSOLUTE MAXIMUM RATINGS (1)(2)(3) SupplyVoltage(VCC ) +250V BiasVoltage(VBB ) +16V InputVoltage(VIN) -0.5VtoVBB +0.5V IKVoltage(VIK) -0.5Vto+16V StorageTemperatureRange (TSTG ) -65°C to+150°C Lead Temperature(Soldering,<10 sec.) 300°C ESD Tolerance, Human Body Model 2 kV Machine Model 200V JunctionTemperature 150°C θJC (typ) 4.5°C/W (1) Allvoltagesaremeasured withrespecttoGND, unlessotherwisespecified. (2) AbsoluteMaximum Ratingsindicatelimitsbeyond whichdamage tothedevicemay occur. (3) IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexas InstrumentsSalesOffice/Distributorsforavailabilityand specifications. OPERATING RANGES (1) VCC +130V to+230V VBB +7V to+13V VIN 0V to+4.25V VIK 0V toVBB +1V VOUT +40V toVCC –5V Case Temperature See Figure11.Deratepower forTC above 110°C. Do notoperatethepartwithouta heatsink. (1) Operatingratingsindicateconditionsforwhichthedeviceisfunctional,butdo notensurespecificperformancelimits.Forensured specificationsand testconditions,see theElectricalCharacteristics.Datasheetmin/max specificationlimitsareensuredby design,test, orstatisticalanalysis.The ensuredspecificationsapplyonlyforthetestconditionslisted.Some performancecharacteristicsmay change when thedeviceisnotoperatedunderthelistedtestconditions.

ELECTRICAL CHARACTERISTICS

(See Figure3 forTestCircuit) Unlessotherwisenoted:VCC = +220V, VBB = +12V, C L = 10 pF,TC = 40°C. DC Tests:VIN = 2.75VDC AC Tests:Output= 110VPP (80V -190V) at1 MHz LM2432 Symbol Parameter Conditions Units Min Typical Max ICC SupplyCurrent No AC InputSignal,No OutputLoad 12 17 mA IBB BiasCurrent 8 11 mA VOUT, 1 DC OutputVoltage No AC InputSignal,VIN = 2.75VDC 121 126 131 VDC VOUT, 2 DC OutputVoltage No AC InputSignal,VIN = 1.25VDC 199 204 209 VDC AV DC VoltageGain No AC InputSignal –50 –53 –56 LE LinearityError No AC InputSignal(1) 5 % tR RiseTime 10% to90% (2) 10 ns +OS Overshoot See (2) 21 % tF FallTime 90% to10% (2) 8 ns –OS Overshoot See (2) 8 % IKERROR IKCurrentOutputError VCC = 210V,VOUT = 150VDC (1) LinearityErroristhevariationinDC gainfromVIN = 1.15VtoVIN = 4.35V. (2) Inputfromsignalgenerator:tr,tf< 2 ns.SlowerinputstotheLM2432 willchange thetransientresponsecharacteristicsand reduce power dissipation. (3) IKERROR = IK – IOUT ,where IK istheIKcurrentoutputfrompin5 (IK)and IOUT isthecathodecurrentintopin2 (VOUT ).IK iscalculatedby measuringVIK acrossa known resistorvaluebetween pin5 and GND. (4) RefertotheRGB VideoProcessordatasheetforIKleakagecompensation,feedbackoperation,and adjustmentrangeinformation.

2 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 AC TEST CIRCUIT Note:10pF loadincludesparasiticcapacitance. Figure3. TestCircuit Figure3 shows a typicaltestcircuitforevaluationoftheLM2432. Thiscircuitwas designedtotestthetransient responseoftheLM2432 ina 50Ω environmentwithouttheuse ofan expensiveFET probe.On theinputside,a 50Ω pulsegeneratoroutputcan be AC coupledand biasedwithan externalsupplyviatheVADJ input.On the outputside,thetwo 4990Ω resistorsforma 400:1dividerwiththe50Ω resistorand theoscilloscope.A testpoint can be includedforeasy use ofan oscilloscopeprobe.A compensationcapacitorcan be used tocompensate thenetworktoachievea flatfrequencyresponse. Copyright© 2005–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 3 ProductFolderLinks:LM2432

120 125 130 135 140 145 150 OFFSET VOLTAGE (V) SPEED (ns) tf tr 40 50 60 70 80 90 100 CASE TEMPERATURE (ºC) SPEED (ns) tf tr 10 12 14 16 18 20 SPEED (ns) LOAD CAPACITANCE (pF) tf tr 0 1 2 3 4 5 100 125 150 175 200 225 250 VOUT (V) VIN (V) OBSOLETE LM2432 SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (VCC = +220V, VBB = +12V, C L = 10 pF,VOUT = 110VPP (80V − 190V),TestCircuit-Figure3,unlessotherwisespecified) VOUT vs VIN LM2432 Pulse Response Figure4. Figure5. Bandwidth Speed vs Load Capacitance Figure6. Figure7. Speed vs Offset Speed vs Case Temperature Figure8. Figure9.

4 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

POWER DISSIPATION (W) FREQUENCY (MHz) (80% ACTIVE TIME) OBSOLETE LM2432 www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) (VCC = +220V, VBB = +12V, C L = 10 pF,VOUT = 110VPP (80V − 190V),TestCircuit-Figure3,unlessotherwisespecified) Power Dissipationvs Frequency Power DeratingCurve Figure10. Figure11. Cathode Pulse Response Figure12. Copyright© 2005–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 5 ProductFolderLinks:LM2432

SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com THEORY OF OPERATION The LM2432 isa highvoltagemonolithicsinglechannelCRT driversuitableforHDTV applications.The LM2432 typicallyoperateswith220V and 12V power supplies.The partishoused ina staggered7-leadTO-220 molded plasticpower package. The circuitdiagramoftheLM2432 isshown inFigure2.The PNP emitterfollower,Q5, providesinputbuffering. Q1 and Q2 forma fixedgaincascodeamplifierwithresistorsR1 and R2 settingthegainat−53.Emitterfollowers Q3 and Q4 isolatethehighoutputimpedance ofthecascode stagefrom thecapacitanceoftheCRT cathode which decreasesthe sensitivityof the deviceto load capacitance.Q6 providesbiasingto the outputemitter followerstagetoreducecrossoverdistortionatlowsignallevels. The LM2432 has an IK currentoutput(pin5)thatproducesa replicaoftheactualcathodecurrentintoVOUT (pin 2).The IK outputpinisinternallyconnectedtothecollectorofQ4. IfIK feedbackisnotused intheapplication, theIKpinshouldbe connectedtothesame groundas pin3 (GND).Otherwise,theIKoutputcan interfacewitha RGB videoprocessorwithIKfeedbackforautomaticcathodecalibration. NOTE Duringthenon-blankingperiod,videocurrentlevelscan be as highas severalmA, which is much higherthan the referencecurrents(inµA range) produced duringthe IK measurement interval.These highcurrentshave thepotentialtoproducelargevoltagesat the IK outputpin.To avoiddamage to Q4, the IK outputvoltage,VIK, must not exceed +16V (VIKMAX ) . Please see the section“CATHODE CURRENT OUTPUT FOR IK FEEDBACK SYSTEMS ”formore informationon theusage and protectionoftheIKoutput.

6 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 APPLICATION HINTS INTRODUCTION Texas Instrumentsiscommittedto provideapplicationinformationthatassistsour customersinobtainingthe 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 LM2432 performanceistargetedfortheHDTV market.The applicationcircuitsshown inthisdocument to optimizeperformanceand to protectagainstdamage from CRT arcoverare designed specificallyforthe LM2432. Ifanothermember oftheTIDTV CRT Driverfamilyisused,pleaserefertoitsdatasheet. POWER SUPPLY BYPASS Since the LM2432 is a wide bandwidth amplifier,proper power supply bypassingis criticalforoptimum performanceand forrobustnessagainstarcover.Improperpower supplybypassingcan resultinlargeovershoot, ringingoroscillation,and even arcoverfailure.0.1µF capacitorsshouldbe connectedfromthesupplypins,VCC and VBB , to ground usingvery shorttraces.Additionally,a 10 µF or largerelectrolyticcapacitorshouldbe connectedfrombothsupplypinstogroundreasonablyclosetotheLM2432. ARC PROTECTION DuringnormalCRT operation,internalarcingmay occasionallyoccur.Thisfast,highvoltage,highenergypulse can damage theLM2432 outputstagesinceitisDC coupledtothecathode.Ina DC coupledapplication,an externalsparkgap withan arcovervoltageratingof200 to300VDC on thecathodeisNOT recommended. The internalCRT socketsparkgap (1to2 kVDC rating)can sufficientlyreducetheinitialarcovervoltageseen atthe cathode.The outputcircuitshown inFigure13 isdesignedtohelpclamp thevoltageattheoutputoftheLM2432 toa safelevelduringan arcover. Externalarcprotectionclamp diodes,D1 and D2, shouldhave a fasttransientresponse,highpeak currentrating, low seriesimpedance and low shuntcapacitance.1SS83 orequivalentdiodeslikeBAV21 arerecommended. D1 and D2 shouldhave short,low impedance connectionsto VCC and ground respectively.The cathode of D1 shouldhave a veryshortconnectiontoa separateVCC bypass capacitor,C3. The groundconnectionofD2 and the C3 shouldhave a short,directpath to ground.This willsignificantlyreduce the high frequencyvoltage transientsthattheLM2432 wouldbe subjectedtoduringan arcover. ResistorR2, which limitsthe arcovercurrentthatisseen by the diodes,shouldbe a ½ W solidcarbon type resistor.R1 limitsthecurrentintotheLM2432 as wellas thevoltagestressattheoutputsofthedeviceand can be a ¼ W metalorcarbonfilmtyperesistor.HavinglargevalueresistorsforR1 and R2 would be desirable,but thishas the effectof increasingriseand falltimes.InductorL1 iscriticalto reduce the initialhighfrequency voltagelevelsthattheLM2432 would be subjectedto.The inductorwillnotonlyhelpprotectthedevicebutitwill alsohelpminimizeriseand falltimesas wellas minimizeEMI. For properarcprotection,itisimportanttonot omitany ofthearcprotectioncomponents shown inFigure13. Copyright© 2005–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 7 ProductFolderLinks:LM2432

SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com Figure13. Recommended ApplicationCircuit EFFECT OF LOAD CAPACITANCE Figure7 shows the effectof increasedload capacitanceon the speed of the device.The riseand falltime increaseby 7% and 7.5%,respectively,peradditionalpF above 10 pF. EFFECT OF OFFSET Figure8 shows the variationinriseand falltimeswhen the DC offsetof the 110VPP outputswing isvaried between 120V and 150VDC .The risetimeshows a variationoflessthan10% relativetothecenterdatapoint (135VDC ).The falltimeshows a variationof14% relativetothecenterdatapoint. THERMAL CONSIDERATIONS Figure9 shows theperformanceoftheLM2432 as a functionofcase temperature.The figureshows thattherise and falltimesoftheLM2432 increaseby approximately17% and 20%, respectively,as thecase temperature increasesfrom 40°C to90°C. Thiscorrespondstoa speed degradationofonly3.5% and 4.0% forevery10°C riseincase temperature. POWER DISSIPATION AND HEATSINK CALCULATION Worst-Case Power Dissipation Figure10 shows the maximum power dissipationof the LM2432 vs.square wave frequencywhen the device uses VCC of220V and isdrivinga 10 pF loadwith110VPP swing alternatingone pixelon,one pixeloffsignal. Note thatthefrequencyrange shown inthepower dissipationfigureisone-halftheactualpixelfrequency.The graph assumes 80% activetime (deviceoperatingat the specifiedfrequency),which is typicalin a HDTV application.The other20% ofthetimethedeviceisassumed tobe sittingattheblacklevel(190V inthiscase). Under theseworst-casecondition,themaximum power dissipatedby theLM2432 isabout8.9W ataround 30 MHz. Itisimportanttonotethatthispower dissipationisa resultofa highfrequencysquarewave input,whichis unrealisticinpracticalTV applications.The bandwidthoftheinputsourceused todrivetheLM2432 was over 300 MHz. Usinga RGB videoprocessororpreamplifierwithlessbandwidthmay cause theLM2432 todissipate lesspower thanshown inFigure10 atthesame conditions. A PracticalApproach toPower Dissipation The power curve (Figure10) mentioned previouslyshows the LM2432 power dissipationforsquare wave frequenciesrangingfrom 1 to50 MHz at110VPP swing.Inpractice,itisunrealisticfora TV todisplayaverage frequencycontentovertheentirepictureexceeding20 MHz. Therefore,itisimportanttoestablishtheworst-case pictureconditionunder normal viewingto givea realisticmaximum power dissipationforthe LM2432. Here is one approach:

8 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 A HDTV signalgeneratorpatternthatyieldsa practicalworst-casepictureconditionisa “multi-burst”patternthat consistsofa 1-to-30MHz sinewave sweep overeach oftheactivelines.The power dissipatedby theLM2432 as a resultofthispictureconditioncan be approximatedby takingtheaverageofthepower between 1 to30 MHz inFigure10.Thisaverageis7W. Because a squarewave inputwas used togeneratethispower curve,a sinewave would cause theLM2432 todissipateslightlylesspower,probablyabout6.7W. Thisisone common way todeterminea practicalfigureformaximum power dissipation.Itisthesystem designer'sresponsibilityto establishthe worst-casepictureconditionforhis particularapplicationand measure dissipationunder that conditiontochoose a properheatsink. HeatsinkCalculationExample Once themaximum dissipationisknown, Figure11 can be used todeterminetheheatsinkrequirementforthe LM2432. Ifthe1-to-30MHz multi-bursttestdescribedpreviouslyisassumed tobe worst-casepicturecondition thatyieldsmaximum dissipation,thentheLM2432 willdissipateabout6.7W. The power deratingcurveshows thatthe maximum allowedcase temperatureis 120°C when 6.7W is dissipated.Ifthe maximum expected ambient temperatureis 65°C, then the maximum thermalresistancefrom devicecase-to-sink(θCS ) can be calculated: θCS = (TCMAX – TAMAX )/PDMAX (1) Thisexample assumes a capacitiveloadof10 pF and no resistiveload.The designershouldnotethatifoutput swing,VCC supplyvoltage,inputbandwidth,orloadcapacitanceisincreased,thentheAC component ofthetotal power dissipationwillalsoincrease. TipsforReducing Power Dissipation The followingmethods can be used toreducethepower dissipatedby theLM2432 inordertooptimizeheatsink sizeand cost:

• Use a lowerVCC supplyvoltagewhilemaintainingsufficientoperatingrange forcutoff,brightness,and drive adjustments.
• Reduce theinputbandwidthtotheLM2432 whilemaintainingacceptablepictureperformance.
• Lower themaximum VPP swingwhilemaintainingacceptablepicturecontrastand brightness.
• Minimizecapacitiveloadon theLM2432 outputby usinggood PCB layoutpractices. OPTIMIZING TRANSIENT RESPONSE Referringto Figure13, 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# 78FR_ _k)were used foroptimizingtheperformanceofthedevicein theTIapplicationboard.The valuesshown inFigure16 can be used as a good startingpointfortheevaluation oftheLM2432. Usinga variableresistorforR1 willsimplifyfindingthevalueneeded foroptimum performancein a givenapplication.Once the optimum valueisdetermined,the variableresistorcan be replacedwitha fixed value. Figure12 shows a typicalcathodepulseresponsewithan outputswingof110VPP usinga RGB videoprocessor thatprovidesinputspeeds with12 ns riseand falltimes. NOTE The RGB processor'ssharpnessfeatureadds emphasis(preshootsand overshoots)tothe risingand fallingedges of the inputpulse,which consequentlyadds emphasis to the cathodepulseresponse. Copyright© 2005–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 9 ProductFolderLinks:LM2432

IK, R VIN VOUT KR To IK interface circuit or RGB SURFHVVRU¶V,. voltage input D PROT IK current from other two LM2432s IK, R + IK, G OBSOLETE LM2432 SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com CATHODE CURRENT OUTPUT FOR IK FEEDBACK SYSTEMS IK Feedback Systems IK feedbackwas developedtoaccuratelybiastheCRT and continuouslycalibrateittothecorrectcut-offand/or drivelevelsovertheusefullifeoftheCRT. RGB videoprocessorsthatuse IK feedbacktoautomaticallyadjust onlycut-off,or blacklevel,are realizedby a 1-pointcalibrationsystem.A few tradenames forthissystem are Auto KineBias(AKB) and BlackCurrentStabilization(BCS).RGB processorsthatcan automaticallyadjustboth cut-offand drive,or whitelevel,are realizedby a 2-pointcalibrationsystem.This is commonly known as ContinuousCathode Calibration(CCC).For convenience,some 2-pointRGB processorsmay be programmed to 1-pointoperationifdrivecalibrationisnotrequired.The LM2432 iscompatiblewithboth1-and 2-pointsystems. To be compatiblewithvariousRGB processors,an interfacecircuitmay be needed inthefeedbackpathbetween theLM2432 IK outputand theprocessor'sIK input.Thisfeedbackcircuitdepends on theRGB processorand feedbacktopology(voltageor current)used.Because each processorhas itsown IK inputsignaland topology requirements,itisoutsidethe scope of thisdata sheetto describeeach feedbackcircuitindetail.For more information,pleaserefertotheRGB processordatasheetorcontactyourlocalTISalesOfficewithyourspecific applicationrequirements. Feedback Topologies RGB processorsthatuse voltagefeedback requirethe LM2432 IK currentto be convertedto voltageviaa resistor(RIK) toground.ThisIK voltage,VIK,willbe fedback totheIK inputoftheRGB processorthroughan interfacecircuit,whichwillbe AC orDC coupleddependingon theprocessor'sIK inputrequirement.For proper feedbackoperation,some processorsmay requirean emitterfollowerto isolatethe IK inputfrom the high impedance oftheresistor.Duringtheclosed-loopIK measurement interval,theIK inputvoltagewillbe sampled and compared withtheprocessor'sinternalreferencevoltagetoautomaticallycalibratethevideolevelsforthe nextfield.The valueofR IK iscrucial,sinceitestablishestheIK voltageand consequently,theoperatingpointof the CRT. Once a stableoperatingpointisestablishedwitha properlychosen resistor,thispointcan be fine- tunedusingtheadjustmentrangeoftheprocessor'sRGB cut-offand/orgaincontrolsviatheI2C-bus.AftertheIK measurement interval(usuallyattheend ofblanking),normalvideowillresume and highcurrentswillflowoutof theIK output.These highvideocurrentswillproducelargeIK voltagesacrosstheresistorthatcan exceed the maximum voltageratingforVIK.Therefore,itisrecommended touse a high-speeddiode(DPROT ) toclamp the LM2432 IK outputtoa safelevel(preferablyVBB ora lowersupply).Ifa zenerdiodeisused instead,itmay be necessaryforthe RGB processorto have IK leakagecompensationforthe leakagecurrentattributedto the zener.Lastly,itispossibleto use a singleR IK resistorto set the IK voltageforallthreeLM2432s. See a simplifiedvoltagefeedbackinterfacecircuitinFigure14. Figure14. SimplifiedIK InterfaceforVoltageFeedback Systems RGB processorsthatuse currentfeedback do notrequirevoltageconversion.The LM2432 IK currentcan be fed back directlyto the IK inputof the RGB processor,althoughsome protectioncircuitrywillbe needed to protecttheRGB processorand LM2432. Duringtheclosed-loopIKmeasurement interval,thevoltageoftheRGB processor'sIK pin willbe internallyclamped, and the IK currentwillbe sampled and compared withthe processor'sinternalreferencecurrenttocalibratethevideolevels.The operatingpointoftheCRT can be fine- tuned usingthe adjustmentrange of the processor'sRGB cut-offand/orgaincontrolsviathe I2C-bus.When

10 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

IK, R VIN VOUT KR To IK interface circuit or RGB SURFHVVRU¶V,. current input D PROT VIK IK current from other two LM2432s IK,G/B OBSOLETE LM2432 www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 normalvideoresumes,a protectionelementshouldshunthighvideocurrentaway fromtheIK inputoftheRGB processor.Sincetheprocessor'sIK pinisnotclamped duringnormalvideo,VIK oftheLM2432 must notexceed +16V (VIKMAX ).A properlychosen highspeed,low-leakagezenerdiode(DPROT )can be used toprotectboththe RGB processorinputand LM2432 IK outputinthiscase.Again,itmay be necessaryfortheRGB processorto have IK leakagecompensationfortheleakagecurrentattributedtothezener.See a simplifiedcurrentfeedback interfacecircuitinFigure15. Figure15. SimplifiedIK InterfaceforCurrentFeedback Systems LM2432 IK Output and ProtectionRequirements The LM2432 IK outputsourcesa copy oftheactualcathodecurrenttotheinterfacecircuitduringtheclosed-loop IK measurement intervaland duringnormalvideowhen theIK feedbackloopisopened.Because thecathode currentduringnormal video is much higherthan the low currentbeing measured duringthe measurement interval,VIK may exceed it'smaximum rating.To protectand preventimproperoperationoftheLM2432, VIK must be maintainedwithintherangespecifiedintheOperatingRanges. For voltagefeedbacktopologies,itisrecommended touse a high-speeddiodetoclamp theIK voltagetoVBB or a lowersupplyduringnormalvideo.A smallseriesresistor(RD inFigure14)can be placedattheIK pintolimit the currentthroughthe diode when clamping.See the TI DemonstrationBoard foran example.For current feedbacktopologies,itisrecommended touse a high-speed,low-leakagezenerdiodetoclamp VIK toa properly chosen zener voltageand shuntthe highvideocurrentaway from the RGB processor'sIK input.The zener voltageshouldbe higherthan the clampingvoltageof the processor'sIK pin and lowerthan the maximum voltageratingofeithertheprocessor'sIKpinorLM2432 VIK,whicheverisless. Ina Direct-ViewTV applicationwitha singleneck PCB, itispossibleforthethreeLM2432 IK outputstoshare the one feedbackcircuitand protectiondiodeby connectingthe IK pinstogetheron the neck PCB. Thiswill reduce component count.In a Rear-ProjectionTV applicationwiththreeneck PCBs, the IK pins can be connectedon thecentralneck PCB ortheRGB processormainboardthroughcabling.Thisway, theycan share theinterfacecircuittofeedback theIK voltageorcurrentsignaltotheRGB processor.However,each LM2432 IKoutputshouldhave itsown protectiondiodeon itsPCB. PC BOARD LAYOUT CONSIDERATIONS For optimum performance,an adequateground plane,isolationbetween channels,good supplybypassingand minimizingunwanted feedbackare necessary.Also,thelengthofthesignaltracesfrom thepreamplifiertothe LM2432 and fromtheLM2432 totheCRT cathodeshouldbe as shortas possible.The followingreferencesare recommended: Ott,Henry W.,“NoiseReductionTechniquesinElectronicSystems”,John Wiley& Sons,New York,1976. “VideoAmplifierDesignforComputer Monitors”,TIApplicationNote 1013. Pease,RobertA.,“TroubleshootingAnalogCircuits”,Butterworth-Heinemann,1991. Because ofitshighsmallsignalbandwidth,thepartmay oscillateina TV iffeedbackoccursaround thevideo channelthroughthechassiswiring.To preventthis,leadstothevideoamplifierinputcircuitshouldbe shielded, and inputcircuitwiringshouldbe spaced as faras possiblefromoutputcircuitwiring. Copyright© 2005–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 11 ProductFolderLinks:LM2432

SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com TYPICAL APPLICATION The highbandwidth,largeswing capability,and simpleapplicationmake theLM2432 idealforRear-Projection and Direct-ViewHDTV CRT applications.The IK outputcan be made compatiblewithany RGB videoprocessor withIK feedback.IftheIK outputisnotused intheapplication,itshouldbe connectedtothesame groundas pin 3 (GND). See the section“CATHODE CURRENT OUTPUT FOR IK FEEDBACK SYSTEMS ” for more information. TIDEMONSTRATION BOARD Figure16 and Figure17 show theschematicand PCB layoutfortheTI demonstrationneck board fora typical Rear-ProjectionHDTV applicationwithIK feedback.Thissinglechannelneck board couldbe used forallthree channels,sinceeach neck board receivesvideo-relatedsignalsdirectlyfrom the RGB mainboard.The power suppliesaredaisy-chainedbetween each channelusinginboardand outboardconnectorsJ6 and J7.Thisboard providesa good example of a layoutthatcan be used as a guide forfuturelayouts.Samples of the TI demonstrationneck boardareavailableupon requesttoyourlocalTISalesOffice. InputVideo Interface On theRGB mainboard,thevideooutputoftheRGB processorisbufferedwitha PNP transistortodrivethe videothroughflatcablingto the TI neck board.The cablingfrom the mainboard plugsintothe neck board at connectorJ8 tosupplyitwithvideo,IK,GND, and othersignals.Between thevideoinput(pin3) ofJ8 and VIN (pin7) oftheLM2432 isanotherbufferstageconsistingoftwo NPN transistors.Both NPN transistorsdrop the videolevelsfrom theprecedingPNP bufferby a totaloftwo VBE .Thisshiftsthenominalinputblacklevelsuch thatthe LM2432 output(orcathode)blacklevelvoltageisnear the nominalcut-offvoltageof the CRT. The overallvoltageshiftfromtheprocessoroutputtotheLM2432 inputisone VBE drop. NOTE The same videolevelshiftingcouldhave been accomplishedusingone NPN bufferon the RGB mainboard to drivethe processor'svideo outputthroughcablingdirectlyto the LM2432 input.However, itwas decidedto preservethe TV's originalRGB mainboard circuitry(thePNP buffer)and use two NPN transistorson theneck board. The inputstage from the RGB processorto the LM2432 willbe determinedby the system designerforhis specificapplication.The inputstagerequireddepends mainlyon thefollowingsystemparameters:

• NominalCRT cut-offvoltage
• NominalblackleveloutputvoltageoftheRGB processor
• VCC & VBB supplyvoltagesoftheLM2432 (determinesDC transfercharacteristic) Once thenominalblacklevelinputtotheLM2432 establishesa cathodeblacklevelneartheCRT cut-offvoltage, itcan be fine-tunedusingthe processor'scut-offadjustmentor calibratedautomaticallyusingthe IK feedback system,ifapplicable.Lastly,some RGB processorvideooutputscannotadequatelydrivethe capacitiveload introducedby the cablingbetween the RGB mainboard and neck boards.To preventloadingthe processor's output,a NPN orPNP bufferstagecan be appliedclosetotheoutputon themainboardtosufficientlydrivethe videosignalthroughcablingto the neck board.Itisimportantto biasthe bufferstage(s)properlyto obtain optimalvideoperformanceand maintainthefullvideoadjustmentrangeoftheRGB processor. Video Output and Arc Protection The routingof the LM2432 outputto the CRT is very criticalto achieve optimalvideo performanceand robustnessagainstarcover.Figure17 shows the routingand component placementfrom VOUT (pin2) of the LM2432 tothecathodepinoftheCRT socket.The components are placedso thatthereisa short,directpath from theLM2432 outputtothecathode.Thisisdone toreducethePCB parasiticcapacitanceon theLM2432 outputand minimizeEMI. Note alsothatL3,D3, D4, and R6 areplacedtominimizethesizeofthevideonodes thattheyareattachedto.Thisenhances theeffectivenessofthearcprotectiondiodes.The anode ofprotection diodeD3 isconnecteddirectlyto a sectionof the ground planethathas a short,directpath to ground.The

12 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 cathode of D4 isconnectedto VCC very closeto decouplingcapacitorC7, which isconnectedto the same sectionoftheground planeas D3. The diodeplacementand routingisveryimportanttoshuntarcovercurrent away from the outputand minimizethe voltagestresson the LM2432. The internalCRT socketsparkgap is essentialtosignificantlyreducetheinitialarcovervoltageseen atthecathode.The DAG connectorshouldbe connectedtoCRT groundforarcreturncurrent. IK Feedback Circuit The TIdemonstrationneck boardwas made so thatno modificationstotheexistingTV circuitrywere necessary (exceptforreplacingthe originalneck boards).Therefore,the video interfaceand IK feedback circuitsare designedtobe compatiblewiththoseoriginalTV circuits.ReferringtoFigure16,theLM2432 IK output(pin5)is connectedtoprotectioncircuitrybeforetheIK currentsignalisroutedtopin4 ofconnectorJ8.Diode D1 protects theLM2432 IK pinfromexcessivevoltageduringnormalvideoby clampingtotheVBB supply.Diode D2 isolates theIK outputfromtheotherchannelsduringtheactiveIK measurement interval.ResistorsR17 and R12 limitthe currentthroughD1 and D2, and C12 isused forfiltering.From connectorJ8,the IK currentsignalispassed throughcablingand combined withtheothertwo IKsignalson theRGB mainboard. NOTE The followingparagraphdescribescircuitrythatisnotpartoftheTI demonstrationneck board.The RGB processor,which operateswitha voltagefeedbackIK topology,uses a single“IK resistor” on theRGB mainboardtoconvertallthreeIK currentsintoa voltage signal.The IK voltagesignalisthenbufferedthrougha PNP transistorbeforeitisfiltered and AC coupledto the RGB processor'sIK input.Thisisone implementationof the IK feedbackcircuitbased on thisTV'sspecificRGB processor.The system designershould referto the RGB processordata sheet to determinethe appropriatefeedback circuit implementationforhisapplication. Supply Decoupling Note thelocationofthefollowingcomponents:

• C5 — VCC bypasscapacitorwithshorttracestotheVCC and GND pinsofLM2432.
• C7 — VCC bypasscapacitorwithshorttracestotheVCC arcprotectiondiodeand ground.Thiscapacitorisvery importantforarcprotection.
• C9 — VBB bypasscapacitorwithshorttracestotheVBB and GND pins.
• C10 and C11 — VCC and VBB electrolyticcapacitorsplacednearsupplypinsofLM2432. Other Items ConnectorJ1 and switchesJP2 & JP4 can be used to bypass the TV's internal200V and 12V suppliesand evaluatethe LM2432 withexternalVCC and VBB supplies.Also,thisdemonstrationboard uses medium-sized PCB holesto accommodate socketpins,which functionto allowformultipleinsertionsof the LM2432 in a convenientmanner. To benefitfrom the enhanced LM2432 package withthinleads,the deviceshould be securedwithsolderinsmallPCB holestooptimizethemetal-to-metalspacingbetween theleads. Copyright© 2005–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 13 ProductFolderLinks:LM2432

SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com Figure16. LM2432 DemonstrationBoard Schematic

14 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

www.ti.com SNOSAL4E –MARCH 2005–REVISED APRIL 2013 Figure17. LM2432 DemonstrationBoard Layout Copyright© 2005–2013,Texas InstrumentsIncorporated SubmitDocumentationFeedback 15 ProductFolderLinks:LM2432

SNOSAL4E –MARCH 2005–REVISED APRIL 2013 www.ti.com

REVISION HISTORY

Changes from RevisionD (April2013)toRevisionE Page

16 SubmitDocumentationFeedback Copyright© 2005–2013,Texas InstrumentsIncorporated

ProductFolderLinks:LM2432

Texas InstrumentsIncorporatedand itssubsidiaries(TI)reservetherighttomake corrections,enhancements,improvementsand other changes toitssemiconductorproductsand servicesperJESD46, latestissue,and todiscontinueany productorserviceperJESD48, latest issue.Buyersshouldobtainthelatestrelevantinformationbeforeplacingordersand shouldverifythatsuch informationiscurrentand complete.Allsemiconductorproducts(alsoreferredtohereinas “components”)aresoldsubjecttoTI’s termsand conditionsofsale suppliedatthetimeoforderacknowledgment. TIwarrantsperformanceofitscomponents tothespecificationsapplicableatthetimeofsale,inaccordancewiththewarrantyinTI’s terms and conditionsofsaleofsemiconductorproducts.Testingand otherqualitycontroltechniquesareused totheextentTIdeems necessary tosupportthiswarranty.Exceptwhere mandated by applicablelaw,testingofallparametersofeach component isnotnecessarily performed. TIassumes no liabilityforapplicationsassistanceorthedesignofBuyers’products.Buyersareresponsiblefortheirproductsand applicationsusingTIcomponents.To minimizetherisksassociatedwithBuyers’productsand applications,Buyersshouldprovide adequatedesignand operatingsafeguards. TIdoes notwarrantorrepresentthatany license,eitherexpressorimplied,isgrantedunderany patentright,copyright,mask work right,or otherintellectualpropertyrightrelatingtoany combination,machine,orprocessinwhichTIcomponents orservicesareused.Information publishedby TIregardingthird-partyproductsorservicesdoes notconstitutea licensetouse such productsorservicesora warrantyor endorsementthereof.Use ofsuch informationmay requirea licensefroma thirdpartyunderthepatentsorotherintellectualpropertyofthe thirdparty,ora licensefromTIunderthepatentsorotherintellectualpropertyofTI. ReproductionofsignificantportionsofTIinformationinTIdatabooks ordatasheetsispermissibleonlyifreproductioniswithoutalteration and isaccompaniedby allassociatedwarranties,conditions,limitations,and notices.TIisnotresponsibleorliableforsuch altered documentation.Informationofthirdpartiesmay be subjecttoadditionalrestrictions. ResaleofTIcomponents orserviceswithstatementsdifferentfromorbeyond theparametersstatedby TIforthatcomponent orservice voidsallexpressand any impliedwarrantiesfortheassociatedTIcomponent orserviceand isan unfairand deceptivebusinesspractice. TIisnotresponsibleorliableforany such statements. Buyeracknowledgesand agreesthatitissolelyresponsibleforcompliancewithalllegal,regulatoryand safety-relatedrequirements concerningitsproducts,and any use ofTIcomponents initsapplications,notwithstandingany applications-relatedinformationorsupport thatmay be providedby TI.Buyerrepresentsand agreesthatithas allthenecessaryexpertisetocreateand implementsafeguardswhich anticipatedangerousconsequencesoffailures,monitorfailuresand theirconsequences,lessenthelikelihoodoffailuresthatmightcause harm and takeappropriateremedialactions.BuyerwillfullyindemnifyTIand itsrepresentativesagainstany damages arisingoutoftheuse ofany TIcomponents insafety-criticalapplications. Insome cases,TIcomponents may be promotedspecificallytofacilitatesafety-relatedapplications.Withsuch components,TI’s goalisto helpenablecustomerstodesignand createtheirown end-productsolutionsthatmeet applicablefunctionalsafetystandardsand requirements.Nonetheless,such components aresubjecttotheseterms. No TIcomponents areauthorizedforuse inFDA ClassIII(orsimilarlife-criticalmedicalequipment)unlessauthorizedofficersoftheparties have executeda specialagreementspecificallygoverningsuch use. OnlythoseTIcomponents whichTIhas specificallydesignatedas militarygradeor“enhanced plastic”aredesignedand intendedforuse in military/aerospaceapplicationsorenvironments.Buyeracknowledgesand agreesthatany militaryoraerospaceuse ofTIcomponents whichhave not been so designatedissolelyattheBuyer's risk,and thatBuyerissolelyresponsibleforcompliancewithalllegaland regulatoryrequirementsinconnectionwithsuch use. TIhas specificallydesignatedcertaincomponents as meetingISO/TS16949 requirements,mainlyforautomotiveuse.Inany case ofuse of non-designatedproducts,TIwillnotbe responsibleforany failuretomeet ISO/TS16949. Products Applications Audio www.ti.com/audio Automotiveand Transportationwww.ti.com/automotive Amplifiers amplifier.ti.com Communicationsand Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP ® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energyand Lighting www.ti.com/energy Clocksand Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space,Avionicsand Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Videoand Imaging www.ti.com/video RFID www.ti-rfid.com OMAP ApplicationsProcessors www.ti.com/omap TIE2E Community e2e.ti.com WirelessConnectivity www.ti.com/wirelessconnectivity MailingAddress:Texas Instruments,PostOfficeBox 655303,Dallas,Texas 75265 Copyright© 2013,Texas InstrumentsIncorporated