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2024-07-28 作者:
LM3915
LM3915 Dot/Bar Display Driver
Literature Number: SNVS740B
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LM3915
Dot/BarDisplayDriver
GeneralDescription
TheLM3915isamonolithicintegratedcircuitthatsensesanalogvoltagelevelsanddrivestenLEDs,LCDsorvacuumfluorescentdisplays,providingalogarithmic3dB/rentdriveisregulatedandprogrammable,ledisplaysystemcanoperatefromasinglesupplyaslowas3Vorashighas25V.
TheICcontainsr,itneedsnoprotectionagainstinputsof±utbuffcyistypicallybetterthan1dB.
TheLM3915’s3dB/stepdisplayissuitedforsignalswithwidedynamicrange,suchasaudiolevel,power,pplicationsincludeaverageorpeaklevelindicators,ingconventionalmeterswithanLEDbargraphresultsinafasterresponding,moreruggeddisplaywithhighvisibilitythatretainstheeaseofinterpretationofananalogdisplay.
ghtnessiseasilycontrolledwithasinglepot.
putscandriveLCDs,le3915scanalsobecascadedwithLM3914sforalinear/logdisplayorwithLM3916sforanextended-rangeVUmeter.
Features
3dB/step,30dBrange
DrivesLEDs,LCDs,orvacuumfluorescents
BarordotdisplaymodeexternallyselectablebyuserExpandabletodisplaysof90dB
Internalvoltagereferencefrom1.2Vto12VOperateswithsinglesupplyof3Vto25VInputsoperatedowntoground
Outputcurrentprogrammablefrom1mAto30mA
Inputwithstands±35VwithoutdamageorfalseoutputsOutputsarecurrentregulated,opencollectorsDirectlydrivesTTLorCMOS
Theinternal10-stepdividerisfloatingandcanbereferencedtoawiderangeofvoltages
TheLM3915isratedforoperationfrom0˚Cto+70˚nnnnnn
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0Vto10VLogDisplay
00510
Notes:CapacitorC1isrequiredifleadstotheLEDsupplyare6"orlonger.
mode,stbekeptbelow7VordroppingresistorshouldbeusedtolimitIdissipation.
2
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pleasecontacttheNationalSemiconductorSalesOffice/issipation(Note6)
MoldedDIP(N)SupplyVoltage
VoltageonOutputDrivers
1365mW
25V25V
ReferenceLoadCurrentStorageTemperatureRangeLeadTemperature(Soldering,10sec.)
10mA
−55˚Cto+150˚C
260˚C
ElectricalCharacteristics(Notes2,4)
Parameter
COMPARATOR
OffsetVoltage,BufferandFirstComparator
OffsetVoltage,BufferandAnyOtherComparatorGain(∆ILED/∆VIN)
InputBiasCurrent(atPin5)InputSignalOvervoltageVOLTAGE-DIVIDERDividerResistance
RelativeAccuracy(InputChangeBetweenAnyTwoThresholdPoints)
AbsoluteAccuracyatEachThresholdPoint
Total,Pin6to4(Note3)(Note3)VIN=−3,−6dBVIN=−9dB
VIN=−12,−15,−18dBVIH=−21,−24,−27dB
VOLTAGEREFERENCEOutputVoltageLineRegulationLoadRegulation
OutputVoltageChangewithTemperatureAdjustPinCurrentOUTPUTDRIVERSLEDCurrent
LEDCurrentDifference(BetweenLargestandSmallestLEDCurrents)LEDCurrentRegulationDropoutVoltageSaturationVoltage
OutputLeakage,EachCollectorOutputLeakagePins10–18Pin1
V
+Conditions(Note2)
0V≤VRLO=VRHI≤12V,ILED=1mA
0V≤VRLO=VRHI≤12V,ILED=1mA
IL(REF)=2mA,ILED=10mA0V≤VIN≤(V+−1.5V)NoChangeinDisplay
MinTypMaxUnits
33
3−35162.0
283.0825
1015
mVmVmA/mV
10035364.0
nAVkΩdB
−0.5−0.5−0.5−0.5
+0.5+0.65+1.0+1.5
dBdBdBdB
0.1mA≤IL(REF)≤4mA,V+=VLED=5V3V≤V+≤18V
0.1mA≤IL(REF)≤4mA,V+=VLED=5V
0˚C≤TA≤+70˚C,IL(REF)=1mA,V+=VLED=5V
1.21.280.010.4175
1.340.032
V%/V%%
120130.430.2531.5
µAmAmAmAVVµAµAµA
=VLED=5V,IL(REF)=1mA
7100.121.20.11
VLED=5V,ILED=2mAVLED=5V,ILED20mA2V≤VLED≤17V,ILED=2mAILED=20mA
ILED(ON)=20mA,@VLED=5V,∆ILED=2mA
ILED=2.0mA,IL(REF)=0.4mA(BarMode)(Note5)(DotMode)(Note5)
0.150.10.1
60
150
0.41010450
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SUPPLYCURRENTStandbySupplyCurrent(AllOutputsOff)
V+=+5V,IL(REF)=0.2mAV+=+20V,IL(REF)=1.0mA
2.46.1
4.29.2
Note1:AbsoluteMingRatingsindicateconditionsforwhichthefunctional,icalCharacteristicsstateDCandACelectricalspecificatioicationsarenotguaranteedforparameterswhereisgiven,however,2:Unlessotherwisestated,allspecificationsapplywiththefollowingconditions:3VDC≤V+≤20VDC3VDC≤VLED≤
V+
−0.015V≤VRHI≤12VDC
−0.015V≤VRLO≤12VDCVREF,VRHI,VRLO≤
0V≤VIN≤
(V+
−1.5V)V+
−1.5V
TA=25˚C,IL(REF)=0.2mA,pin9connectedtopin3(barmode).Forhigherpowerdissipations,pulsetestingisused.
Note3:Accuracyismeasuredreferredto0dB=+10.000VDCatpin5,with+10.000VDCatpin6,rfullscalevoltages,leforthresholdvoltages.
Note4:Pin5inputcurrentmustbelimitedto±itionofa39kresistorinserieswithpin5allows±100Vsignalswithoutdamage.
Note5:Barmoderesultswhenpin9iswithin20mVofV+.Dotmoderesultswhenpin9ispulledatleast200mVbelowV+.LED#10(pin10outputcudisabledifpin9ispulled0.9VormorebelowVLED.
Note6:ThemaximumjunctiontemperatureoftheLM3915is100˚ontoambienresistanceis55˚C/WforthemoldedDIP(Npackage).
ThresholdVoltage(Note3)
Output
12345
dB−27−24−21−18−15
Min0.4220.5960.8411.1891.679
Typ0.4470.6310.8911.2591.778
Max0.5310.7501.0591.4131.995
Output
678910
dB−12−9−6−30
Min2.3723.3504.7326.6839.985
Typ2.5123.5485.0127.07910
2
3
5
7
1
4
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SupplyCurrentvsTemperatureOperatingInputBiasCurrentvsTemperature
10435
ReferenceVoltagevs
TemperatureReferenceAdjustPinCurrentvsTemperature
00510436
00510437
LEDCurrent-Regulation
DropoutLEDDriverSaturation
Voltage
00510438
00510439
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InputCurrentBeyondSignalRange(Pin5)LEDCurrentvsReferenceLoading
00510440
00510441
LEDDriverCurrent
RegulationTotalDividerResistance
vsTemperature
00510442
00510443
Common-ModeLimitsOutputCharacteristics
00510444
00510445
6
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00510404
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generalideaofthecircuit’nputimped-ancebufferoperateswithsignalsfromgroundto12V,-nalisthenappliedtoaseriesof10comparators;eachofwhichisbiasedtoadifferentcomparisonlevelbytheresistorstring.
Intheexampleillustrated,case,foreach3dBthattheinputsignalincreases,sistordividercanbecon-nectedbetweenany2voltages,providingthattheyareatleast1.5VbelowV+andnolowerthanV−.INTERNALVOLTAGEREFERENCE
Thereferenceisdesignedtobeadjustableanddevelopsanominal1.25VbetweentheREFOUT(pin7)andREFADJ(pin8)erencevoltageisimpressedacrossprogramresistorR1and,sincethevoltageisconstant,aconstantcurrentI1thenflowsthroughtheoutputsetresistorR2givinganoutputvoltageof:
00510406
Outputsmayberuectiverationresistanceoftheoutputtransistors,equaltoRthetransistors’collectorresistance,isabout50Ω.ItpossibletodriveLEDsfromrectifiedACwithnofilteravoidoscillations,theLEDsupplyshouldbebypassed2.2µFtantalumor10µFaluminumelectrolyticcapac
00510405
MODEPINUSE
Pin9,theModeSelectinput,permitschainingofmLM3915s,andcontrolsbarordotmodeoperationfollowingtabulationshowsthebasicwaysofusingthisOthermorecomplexuseswillbeillustratedintheations.
BarGraphDisplay:WireModeSelect(pin9)directly3(V+pin).
DotDisplay,SingleLM3915Driver:LeavetheModepinopencircuit.
DotDisplay,20orMoreLEDs:,theonewiththelowestinputvcomparisonpoints)topin1ofthenexthigherLM3915Continueconnectingpin3915driverinthechainwillhavepin9leftoppreviousdriversshouldhavea20kresistorinparallLED#9(pin11toVLED).
Sincethe120µAcurrent(max)fromtheadjustterminalrepresentsanerrorterm,thereferencewasdesignedtominimizechangesofthiscurrentwithV+rectoperation,referenceloadcurrentshouldbebe-tween80µpacitanceshouldbelessthan0.05µF.
CURRENTPROGRAMMING
Afeaturenotrentdrawnoutofthereferencevoltagepin(pin7)-proximately10timesthiscurrentwillbedrawnthrougheachlightedLED,andthiscurrentwiltdrawnbytheinternal10-resistordivider,aswellasbytheexternalcurrentandvoltlitytomodu-lateLEDbrightnesswithtime,orinproportiontoinputvolt-ageandothersignalscanleadtoanumberofnoveldisplaysorwaysofindicatinginputovervoltages,alarms,etc.
currentisheldatabout10timesthereferenceloadcurrent,independentofoutputvoltageandprocessingvariables,aslongasthetransistorisnotsatu-rated.
8
ModePinFunctionalDescriptio
othefiedblockdiagrambelow.
BlockDiagramofModePinFunction
00510
*Highforbar
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DOTORBARMODESELECTION
Thevoltageatpin9issensedbycomparatorC1,nominallyreferencedto(V+−100mV).Thechipisinbarmodewhenpin9isabovethislevel;otherwiseit’paratorisdesignedsothatpin9canbeleftopencircuitfordotmode.
Takingintoaccountcomparatorgainandvariationinthe100mVreferencelevel,pin9shouldbenomorethan20mVbelowV+forbarmodeandmorethan200mVbelowV+(oropencircuit)applications,pin9iseitheropen(dotmode)ortiedtoV+(barmode).Inbarmode,urrentsdrawnfromthepowersupply(LEDcurrent,forexample)ECARRY
InorderforthedisplaytomakesensewhenmultipleLM3915sarecascadedindotmode,specialcircuitryhasbeenincludedtoshutoffLED#10ofthefirstdevicewhenLED#nectionforcascadingindotmodehasalreadybeendescribedandisdepictedbelow.
AslongastheinputsignalvoltageisbelowthethresholdofthesecondLM3915,LED#9ofLM3915#astheinputvoltagereachesthethresholdofLED#11,pin9ofLM3915#1ispulledanLEDdrop(1.5Vormore)nditionissensedbycomparatorC2,rcestheoutputofC2low,whichshutsoffoutputtransistorQ2,extinguishingLED#10.
ysmallcurrent(lessthan100µA)thatisdivertedfromLED#9doesnotnoticeablyaffectitsintensity.
Anauxiliarycurrentsourceatpin1keepsatleast100µAflowingthroughLED#suresthatpin9ofLM3915#1isheldlowenoughtoforceLED#100µAdoesnotnor-mallyproducesignificantLEDillumination,iisbothersome,thesimplecureistoshuntLED#1VIRdropismorethanthe900mV
OTHERDEVICECHARACTERISTICS
TheLM3915isrelativelylow-powereditself,andsinceanynumberofLEDscanbepoweredfromabout3V,lstandbysupplycurrent(allLEDsOFF)r,anyreferenceloadingadds4timesthatcurrentdraintotheV+(pin3)mple,anLM3916witha1mAreferencepinload(1.3k)wouldsupplyalmost10mAtoeveryLEDwhiledrawingonly10mAfromitsV+-scale,theICistypicallydrawinglessthan10%playdriverdoesnothavebuilt-inhyapidlychangingsignalconditions,“over-lap”ngemaybemuchmorerapidbetweenLED#10ofonedeviceandLED#1ofaseconddevice“chained”tothefirst.
ApplicationHints
ThemostdifficultproblemoccurswhenlargeLEDcurrentsarebeingdrawn,ur-rentsflowingoutofthegroundpincausevoltagedropsinexternalwiring,ngthereturnwiresfromsignalsources,referencegroundandbot-tomoftheresistorstringtoasinglepointverynearpin2isthebestsolution.
ingontheseverityoftheproblem0.05µFto2.2µnodelinewiringisinaccessible,oftensimilardecouplingfrompin1topin2willbesufficient.
IfLEDturnONseemsslow(barmode)orseveralLEDslight(dotmode),swhereproperwiringandbypassingfailtostoposcillations,V+edscalemeterapplicationsmayhaveoneorbothendsofthigh-impedanceendsshouldbebypassedtopin2withatleasta0.001µFcapaci-tor,orupto0.1µFinnoisyenvironments.
CascadingLM3915sinDotMode
00510408
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分销商库存信息:
NATIONAL-SEMICONDUCTORLM3915N-1/NOPB
本文标签: LM3915N1NOPB中文规格书Datasheet资料
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