LM56

LM56

DualOutputLowPowerThermostat

GeneralDescription

TheLM56isaprecisionlowpowerthermostat.Twostabletemperaturetrippoints(VT1andVT2)aregeneratedbydividingdowntheLM561.250Vbandgapvoltagereferenceusing3externalresistors.TheLM56hastwodigitaloutputs.OUT1goesLOWwhenthetemperatureexceedsT1andgoesHIGHwhenthethetemperaturegoesbelow(T1–THYST).Similarly,OUT2goesLOWwhenthetempera-tureexceedsT2andgoesHIGHwhenthetemperaturegoesbelow(T2–THYST).THYSTisaninternallyset5˚Ctypicalhysteresis.

TheLM56isavailableinan8-leadMini-SO8surfacemountpackageandan8-leadsmalloutlinepackage.

Features

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DigitaloutputssupportTTLlogiclevelsInternaltemperaturesensor

2internalcomparatorswithhysteresisInternalvoltagereference

Currentlyavailablein8-pinSOplasticpackageFutureavailabilityinthe8-pinMini-SO8package

KeySpecifications

jPowerSupplyVoltagejPowerSupplyCurrentjVREFjHysteresisTemperaturejInternalTemperature

2.7V–10V230µA(max)1.250V±1%(max)

5˚C

(+6.20mV/˚CxT)+395mV

Applications

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MicroprocessorThermalManagementAppliances

PortableBatteryPowered3.0Vor5VSystemsFanControl

IndustrialProcessControlHVACSystems

RemoteTemperatureSensingElectronicSystemProtection

SensorOutputVoltage

nTemperatureTripPointAccuracy:

LM56BIM

+25˚C

+25˚Cto+85˚C−40˚Cto+125˚C

LM56CIM

±2˚C(max)±2˚C(max)±3˚C(max)±3˚C(max)±3˚C(max)±4˚C(max)

SimplifiedBlockDiagramandConnectionDiagram

DS0123-2

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OrderNumberNS

PackageNumberTransportMediaPackageMarking

LM56BIMM08ASOP-8

LM56BIMXM08ASOP-82500Units

LM56CIMM08ASOP-8

LM56CIMXM08ASOP-82500Units

LM56BIMMMUA08AMSOP-8

LM56BIMMXMUA08AMSOP-83500Units

LM56CIMMMUA08AMSOP-8

LM56CIMMXMUA08AMSOP-83500Units

RailLM56BIM

Tape&ReelLM56BIM

RailLM56CIM

Tape&ReelLM56CIM

RailT02B

Tape&Reel

T02B

RailT02C

Tape&Reel

T02C

©2001NationalSemiconductorCorporationDS0123www.national.com

LM56TypicalApplication

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VT1=1.250Vx(R1)/(R1+R2+R3)

VT2=1.250Vx(R1+R2)/(R1+R2+R3)where:

(R1+R2+R3)=27kΩand

VT1orT2=[6.20mV/˚CxT]+395mVtherefore:R1=VT1/(1.25V)x27kΩ

R2=(VT2/(1.25V)x27kΩ)−R1R3=27kΩ−R1−R2

FIGURE1.MicroprocessorThermalManagement

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LM56AbsoluteMaximumRatings(Note1)

InputVoltage

InputCurrentatanypin(Note2)PackageInputCurrent(Note2)PackageDissipationatTA=25˚C(Note3)

ESDSusceptibility(Note4)HumanBodyModelMachineModelSolderingInformationSOPackage(Note5):

12V5mA20mA900mW1000V200V

VaporPhase(60seconds)Infrared(15seconds)StorageTemperature215˚C220˚C

−65˚Cto+150˚C

OperatingRatings(Note1)

OperatingTemperatureRangeLM56BIM,LM56CIM

PositiveSupplyVoltage(V+)MaximumVOUT1andVOUT2TMIN≤TA≤TMAX−40˚C≤TA≤+125˚C

+2.7Vto+10V

+10V

LM56ElectricalCharacteristics

ThefollowingspecificationsapplyforV+=2.7VDC,andVREFloadcurrent=50µAunlessotherwisespecified.Boldfacelim-itsapplyforTA=TJ=TMINtoTMAX;allotherlimitsTA=TJ=25˚Cunlessotherwisespecified.

Typical

Symbol

TemperatureSensor

TripPointAccuracy(IncludesVREF,ComparatorOffset,andTemperatureSensitivityerrors)TripPointHysteresis

+25˚C≤TA≤+85˚C−40˚C≤TA≤+125˚CTA=−40˚CTA=+25˚CTA=+85˚CTA=+125˚C

InternalTemperatureSensitivity

TemperatureSensitivityErrorOutputImpedanceLineRegulation

−1µA≤IL≤+40µA+3.0V≤V≤+10V,+25˚C≤TA≤+85˚C+3.0V≤V+≤+10V,−40˚C≤TA<25˚C+2.7V≤V+≤+3.3V

VT1andVT2AnalogInputsIBIASVINVOSVREFOutputVREFVREFNominalVREFError

∆VREF/∆V+∆VREF/∆ILLineRegulation

LoadRegulationSourcing

+3.0V≤V+≤+10V+2.7V≤V+≤+3.3V+30µA≤IL≤+50µA

0.130.151.250V

V

AnalogInputBiasCurrentAnalogInputVoltageRangeComparatorOffset

150V−1GND2

8

8

++LM56BIMLimits(Note7)

LM56CIMLimits(Note7)

Units(Limits)

ParameterConditions(Note6)

±2±2±3

4566+6.20

363.56.54.57.548

±3±3±4

363.56.54.57.548

˚C(max)˚C(max)˚C(max)˚C(min)˚C(max)˚C(min)˚C(max)˚C(min)˚C(max)˚C(min)˚C(max)mV/˚C

±2±3

1500

±3±4

1500

˚C(max)˚C(max)Ω(max)mV/V(max)mV/V(max)mV(max)nA(max)

VVmV(max)

±0.36±0.61±2.3

300

±0.36±0.61±2.3

300

±1±12.5

0.251.10.15

±1±12.5

0.251.10.15

%(max)mV(max)mV/V(max)mV(max)mV/µA(max)

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LM56LM56ElectricalCharacteristics

ThefollowingspecificationsapplyforV+=2.7VDC,andVREFloadcurrent=50µAunlessotherwisespecified.Boldfacelim-itsapplyforTA=TJ=TMINtoTMAX;allotherlimitsTA=TJ=25˚Cunlessotherwisespecified.SymbolV+PowerSupplyISDigitalOutputsIOUT(“1”)VOUT(“0”)Logical“1”OutputLeakageCurrent

Logical“0”OutputVoltage

IOUT=+50µA

0.4

V(max)

Note1:AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsforwhichthedeviceisfunctional,butdonotguaranteespecificperformancelimits.Forguaranteedspecificationsandtestconditions,seetheElectricalCharacteristics.Theguaranteedspecificationsapplyonlyforthetestconditionslisted.Someperformancecharacteristicsmaydegradewhenthedeviceisnotoperatedunderthelistedtestconditions.

Note2:Whentheinputvoltage(VI)atanypinexceedsthepowersupply(VIV+),thecurrentatthatpinshouldbelimitedto5mA.The20mAmaximumpackageinputcurrentratinglimitsthenumberofpinsthatcansafelyexceedthepowersupplieswithaninputcurrentof5mAtofour.

Note3:ThemaximumpowerdissipationmustbederatedatelevatedtemperaturesandisdictatedbyTJmax(maximumjunctiontemperature),θJA(junctiontoambientthermalresistance)andTA(ambienttemperature).ThemaximumallowablepowerdissipationatanytemperatureisPD=(TJmax–TA)/θJAorthenumbergivenintheAbsoluteMaximumRatings,whicheverislower.Forthisdevice,TJmax=125˚C.Forthisdevicethetypicalthermalresistance(θJA)ofthedifferentpackagetypeswhenboardmountedfollow:

ParameterConditionsTypical(Note6)

Limits(Note7)2302301

Units(Limits)µA(max)µA(max)µA(max)

SupplyCurrentV+=+10VV+=+2.7VV+=+5.0V

PackageType

M08AMUA08A

θJA110˚C/W250˚C/W

Note4:Thehumanbodymodelisa100pFcapacitordischargethrougha1.5kΩresistorintoeachpin.Themachinemodelisa200pFcapacitordischargeddirectlyintoeachpin.

Note5:SeeAN450“SurfaceMountingMethodsandTheirEffectsonProductReliability”orthesectiontitled“SurfaceMount”foundinanypost1986NationalSemiconductorLinearDataBookforothermethodsofsolderingsurfacemountdevices.Note6:TypicalsareatTJ=TA=25˚Candrepresentmostlikelyparametricnorm.Note7:LimitsareguaranteedtoNational’sAOQL(AverageOutgoingQualityLevel).

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LM56TypicalPerformanceCharacteristics

QuiescentCurrentvsTemperature

VREFOutputVoltagevsLoadCurrent

OUT1andOUT2VoltageLevelsvsLoadCurrent

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TripPointHysteresisvsTemperature

TemperatureSensorOutputVoltagevsTemperature

TemperatureSensorOutputAccuracyvsTemperature

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TripPoint

AccuracyvsTemperature

ComparatorBiasCurrentvsTemperatureOUT1andOUT2LeakageCurrentvsTemperature

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DS0123-11DS0123-12

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LM56TypicalPerformanceCharacteristics

VTEMPOutput

LineRegulationvsTemperature

(Continued)

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VREFStart-UpResponseVTEMPStart-UpResponse

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LM56FunctionalDescription

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1.0V+PINDESCRIPTION

Thisisthepositivesupplyvoltagepin.Thispinshouldbebypassedwith0.1µFcapacitortoground.

Thisisthegroundpin.

Thisisthe1.250Vbandgapvoltagereferenceout-putpin.Inordertomaintaintrippointaccuracythispinshouldsourcea50µAload.

Thisisthetemperaturesensoroutputpin.

Thisisanopencollectordigitaloutput.OUT1isactiveLOW.ItgoesLOWwhenthetemperatureisgreaterthanT1andgoesHIGHwhenthetempera-turedropsbelowT1–5˚C.Thisoutputisnotin-tendedtodirectlydriveafanmotor.

Thisisanopencollectordigitaloutput.OUT2isactiveLOW.ItgoesLOWwhenthetemperatureisgreaterthantheT2setpointandgoesHIGHwhenthetemperatureislessthanT2–5˚C.Thisoutputisnotintendedtodirectlydriveafanmotor.ThisistheinputpinforthetemperaturetrippointvoltageforOUT1.

ThisistheinputpinforthelowtemperaturetrippointvoltageforOUT2.

GNDVREFVTEMPOUT1

OUT2

DS0123-16

VT1VT2VT1=1.250Vx(R1)/(R1+R2+R3)

VT2=1.250Vx(R1+R2)/(R1+R2+R3)where:

(R1+R2+R3)=27kΩand

VT1orT2=[6.20mV/˚CxT]+395mVtherefore:R1=VT1/(1.25V)x27kΩ

R2=(VT2/(1.25V)x27k)Ω–R1R3=27kΩ−R1−R2

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LM56ApplicationHints

2.0LM56TRIPPOINTACCURACYSPECIFICATIONForsimplicitythefollowingisananalysisofthetrippointaccuracyusingthesingleoutputconfigurationshowinFig-ure2withasetpointof82˚C.TripPointErrorVoltage=VTPE,ComparatorOffsetErrorforVT1ETemperatureSensorError=VTSEReferenceOutputError=VREfortheLM56BIM.Notethistrippointerrorspecificationdoesnotincludeanyerrorintroducedbythetoleranceoftheactualresistorsused,noranyerrorintroducedbypowersupplyvariation.

Iftheresistorshavea±0.5%tolerance,anadditionalerrorof±0.4˚Cwillbeintroduced.Thiserrorwillincreaseto±0.8˚Cwhenbothexternalresistorshavea±1%tolerance.3.0BIASCURRENTEFFECTONTRIPPOINTACCURACY

Biascurrentforthecomparatorinputsis300nA(max)each,overthespecifiedtemperaturerangeandwillnotintroduceconsiderableerrorifthesumoftheresistorvaluesarekepttoabout27kΩasshowninthetypicalapplicationofFigure1.Thisbiascurrentofonecomparatorinputwillnotflowifthetemperatureiswellbelowthetrippointlevel.Asthetemperatureapproachestrippointlevelthebiascurrentwillstarttoflowintotheresistornetwork.Whenthetemperaturesensoroutputisequaltothetrippointlevelthebiascurrentwillbe150nA(max).Oncethetemperatureiswellabovethetrippointlevelthebiascurrentwillbe300nA(max).There-fore,thefirsttrippointwillbeaffectedby150nAofbiascurrent.Theleakagecurrentisverysmallwhenthecom-paratorinputtransistorofthedifferentpairisoff(seeFigure3).

Theeffectofthebiascurrentonthefirsttrippointcanbedefinedbythefollowingequations:

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FIGURE2.SingleOutputConfiguration

1.VTPE=±VT1E−VTSE+VREWhere:

2.VT1E=±8mV(max)

3.VTSE=(6.20mV/˚C)x(±3˚C)=±18.6mV4.VRE=1.250Vx(±0.01)R2/(R1+R2)

UsingEquationsfrompage1ofthedatasheet.

VT1=1.25VxR2/(R1+R2)=(6.20mV/˚C)(82˚C)+395mVSolvingforR2/(R1+R2)=0.7227then,

5.VRE=1.250Vx(±0.01)R2/(R1+R2)=(0.0125)x(0.7227)=±9.03mV

Theindividualerrorsdonotaddalgebraicallybecause,theoddsofalltheerrorsbeingattheirextremesarerare.ThisisprovenbythefactthespecificationforthetrippointaccuracystatedintheElectricalCharacteristicforthetemperaturerangeof−40˚Cto+125˚C,forexample,isspecifiedat±3˚C

whereIB=300nA(themaximumspecifiederror).

Theeffectofthebiascurrentonthesecondtrippointcanbedefinedbythefollowingequations:

whereIB=300nA(themaximumspecifiederror).

Thecloserthetwotrippointsaretoeachotherthemoresignificanttheerroris.WorstcasewouldbewhenVT1=VT2=VREF/2.

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LM56ApplicationHints

(Continued)

DS0123-18

FIGURE3.SimplifiedSchematic

4.0MOUNTINGCONSIDERATIONS

ThemajorityofthetemperaturethattheLM56ismeasuringisthetemperatureofitsleads.Therefore,whentheLM56isplacedonaprintedcircuitboard,itisnotsensingthetem-peratureoftheambientair.Itisactuallysensingthetem-peraturedifferenceoftheairandthelandsandprintedcircuitboardthattheleadsareattachedto.Themostaccuratetemperaturesensingisobtainedwhentheambienttempera-tureisequivalenttotheLM56’sleadtemperature.

AswithanyIC,theLM56andaccompanyingwiringandcircuitsmustbekeptinsulatedanddry,toavoidleakageandcorrosion.Thisisespeciallytrueifthecirucitmayoperateatcoldtemperatureswherecondensationcanoccur.Printed-circuitcoatingsandvarnishessuchasHumisealandepoxypaintsordipsareoftenusedtoensurethatmoisturecannotcorrodetheLM56oritsconnections.

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LM56ApplicationHints

5.0

(Continued)

VREFANDVTEMPCAPACTIVELOADING

DS0123-19

FIGURE4.LoadingofVREFandVTEMPTheLM56VREFandVTEMPoutputshandlecapacitiveload-ingwell.Withoutanyspecialprecautions,theseoutputscandriveanycapacitiveloadasshowninFigure4.

6.0NOISYENVIRONMENTS

OverthespecifiedtemperaturerangetheLM56VTEMPout-puthasamaximumoutputimpedanceof1500Ω.Inanextremelynoisyenvironmentitmaybenecessarytoaddsomefilteringtominimizenoisepickup.Itisrecommendedthat0.1µFbeaddedfromV+toGNDtobypassthepowersupplyvoltage,asshowninFigure4.InanoisyenvironmentitmaybenecessarytoaddacapacitorfromtheVTEMPoutputtoground.A1µFoutputcapacitorwiththe1500Ωoutputimpedancewillforma106Hzlowpassfilter.SincethethermaltimeconstantoftheVTEMPoutputismuchslowerthanthe9.4mstimeconstantformedbytheRC,theoverallresponsetimeoftheVTEMPoutputwillnotbesignificantlyaffected.FormuchlargercapacitorsthisadditionaltimelagwillincreasetheoverallresponsetimeoftheLM56.7.0

APPLICATIONSCIRCUITS

whereIB=300nA(themaximumspecifiederror).

ThecurrentshowninFigure6isasimpleovertemperaturedetectorforpowerdevices.Inthisexample,anaudiopoweramplifierICisboltedtoaheatsinkandanLM56CelsiustemperaturesensorismountedonaPCboardthatisboltedtotheheatsinknearthepoweramplifier.Toensurethatthesensingelementisatthesametemperatureastheheatsink,thesensor’sleadsaremountedtopadsthathavefeedthroughstothebacksideofthePCboard.SincetheLM56issensingthetemperatureoftheactualPCboardthebacksideofthePCboardalsohaslargegroundplanetohelpconducttheheattothedevice.Thecomparator’soutputgoeslowiftheheatsinktemperaturerisesaboveathresholdsetbyR1,R2,andthevoltagereference.Thisfaultdetectionoutputfromthecomparatornowcanbeusedtoturnonacoolingfan.Thecircuitasshownindesigntoturnthefanonwhenheatsinktemperatureexceedsabout80˚C,andtoturnthefanoffwhentheheatsinktemperaturefallsbelowap-proximately75˚C.

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ThecircuitshowninFigure5willreducetheeffectivebiascurrenterrorforVT2asdiscussedinSection3.0tobeequivalenttotheerrortermofVT1.Forthiscircuittheeffectofthebiascurrentonthefirsttrippointcanbedefinedbythefollowingequations:

whereIB=300nA(themaximumspecifiederror).Similarly,biascurrentaffectonVT2canbedefinedby:

DS0123-20

FIGURE5.ReducingErrorsCausedbyBiasCurrent

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LM56ApplicationHints

(Continued)

DS0123-21

FIGURE6.AudioPowerAmplifierOvertemperatureDetector

DS0123-22

FIGURE7.SimpleThermostat

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LM56PhysicalDimensions

inches(millimeters)unlessotherwisenoted

8-Lead(0.150\"Wide)MoldedSmallOutlinePackage,JEDECOrderNumberLM56BIM,LM56BIMX,LM56CIMorLM56CIMX

NSPackageNumberM08A

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LM56DualOutputLowPowerThermostatPhysicalDimensions

inches(millimeters)unlessotherwisenoted(Continued)

8-LeadMoldedMiniSmallOutlinePackage(MSOP)

(JEDECREGISTRATIONNUMBERM0-187)

OrderNumberLM56BIMM,LM56BIMMX,LM56CIMM,orLM56CIMMX

NSPackageNumberMUA08A

LIFESUPPORTPOLICY

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

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Tel:1-800-272-9959Fax:1-800-737-7018Email:support@nsc.com

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DeutschTel:+49(0)6995086208EnglishTel:+44(0)8702402171FrançaisTel:+33(0)141918790

2.Acriticalcomponentisanycomponentofalifesupportdeviceorsystemwhosefailuretoperformcanbereasonablyexpectedtocausethefailureofthelifesupportdeviceorsystem,ortoaffectitssafetyoreffectiveness.

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Email:ap.support@nsc.com

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Tel:81-3-5639-7560Fax:81-3-5639-7507

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