文献翻译——温度传感器芯片简化设计

第1页外文文献资料TemperatureSensorICsSimplifyDesignsWhenyousetouttoselectatemperaturesensor,youarenolongerlimitedtoeitherananalogoutputoradigitaloutputdevice.Thereisnowabroadselectionofsensortypes,oneofwhichshouldmatchyoursystemsneeds.Untilrecently,allthetemperaturesensorsonthemarketprovidedanalogoutputs.Thermistors,RTDs,andthermocoupleswerefollowedbyanotheranalog-outputdevice,thesilicontemperaturesensor.Inmostapplications,unfortunately,theseanalog-outputdevicesrequireacomparator,anADC,oranamplifierattheiroutputtomakethemuseful.Thus,whenhigherlevelsofintegrationbecamefeasible,temperaturesensorswithdigitalinterfacesbecameavailable.TheseICsaresoldinavarietyofforms,fromsimpledevicesthatsignalwhenaspecifictemperaturehasbeenexceededtothosethatreportbothremoteandlocaltemperatureswhileprovidingwarningsatprogrammedtemperaturesettings.Thechoicenowisntsimplybetweenanalog-outputanddigital-outputsensors;thereisabroadrangeofsensortypesfromwhichtochoose.ClassesofTemperatureSensorsFourtemperature-sensortypesareillustratedinFigure1.Anidealanalogsensorprovidesanoutputvoltagethatisaperfectlylinearfunctionoftemperature(A).InthedigitalI/Oclassofsensor(B),temperaturedataintheformofmultiple1sand0sarepassedtothemicrocontroller,oftenviaaserialbus.Alongthesamebus,dataaresenttothetemperaturesensorfromthemicrocontroller,usuallytosetthetemperaturelimitatwhichthealertpinsdigitaloutputwilltrip.Alertinterruptsthemicrocontrollerwhenthetemperaturelimithasbeenexceeded.Thistypeofdevicecanalsoprovidefancontrol.Figure1.SensorandICmanufacturerscurrentlyofferfourclassesoftemperaturesensors.Analog-plussensors(C)areavailablewithvarioustypesofdigitaloutputs.TheVOUTversustemperaturecurveisforanICwhosedigitaloutputswitcheswhenaspecifictemperaturehasbeenexceeded.Inthiscase,theplusaddedtotheanalogtemperaturesensorisnothingmorethanacomparatorandavoltagereference.Othertypesofpluspartsshiptemperaturedataintheformofthedelaytimeaftertheparthasbeenstrobed,orintheformofthefrequencyortheperiodofasquarewave,whichwillbediscussedlater.第2页Thesystemmonitor(D)isthemostcomplexICofthefour.InadditiontothefunctionsprovidedbythedigitalI/Otype,thistypeofdevicecommonlymonitorsthesystemsupplyvoltages,providinganalarmwhenvoltagesriseaboveorsinkbelowlimitssetviatheI/Obus.Fanmonitoringand/orcontrolissometimesincludedinthistypeofIC.Insomecases,thisclassofdeviceisusedtodeterminewhetherornotafanisworking.Morecomplexversionscontrolthefanasafunctionofoneormoremeasuredtemperatures.Thesystemmonitorsensorisnotdiscussedherebutisbrieflymentionedtogiveacompletepictureofthetypesoftemperaturesensorsavailable.Analog-OutputTemperatureSensorsThermistorsandsilicontemperaturesensorsarewidelyusedformsofanalog-outputtemperaturesensors.Figure2clearlyshowsthatwhenalinearrelationshipbetweenvoltageandtemperatureisneeded,asilicontemperaturesensorisafarbetterchoicethanathermistor.Overanarrowtemperaturerange,however,thermistorscanprovidereasonablelinearityandgoodsensitivity.Manycircuitsoriginallyconstructedwiththermistorshaveovertimebeenupdatedusingsilicontemperaturesensors.Figure2.Thelinearityofthermistorsandsilicontemperaturesensors,twopopularanalog-outputtemperaturedetectors,iscontrastedsharply.Silicontemperaturesensorscomewithdifferentoutputscalesandoffsets.Some,forexample,areavailablewithoutputtransferfunctionsthatareproportionaltoK,otherstoCorF.SomeoftheCpartsprovideanoffsetsothatnegativetemperaturescanbemonitoredusingasingle-endedsupply.Inmostapplications,theoutputofthesedevicesisfedintoacomparatororanA/Dconvertertoconvertthetemperaturedataintoadigitalformat.Despitetheneedfortheseadditionaldevices,thermistorsandsilicontemperaturesensorscontinuetoenjoypopularityduetolowcostandconvenienceofuseinmanysituations.DigitalI/OTemperatureSensorsAboutfiveyearsago,anewtypeoftemperaturesensorwasintroduced.Thesedevicesincludeadigitalinterfacethatpermitscommunicationwithamicrocontroller.TheinterfaceisusuallyanICorSMBusserialbus,butotherserialinterfacessuchasSPIarecommon.Inadditiontoreportingtemperaturereadingstothemicrocontroller,theinterfacealsoreceives第3页instructionsfromthemicrocontroller.Thoseinstructionsareoftentemperaturelimits,which,ifexceeded,activateadigitalsignalonthetemperaturesensorICthatinterruptsthemicrocontroller.Themicrocontrolleristhenabletoadjustfanspeedorbackoffthespeedofamicroprocessor,forexample,tokeeptemperatureundercontrol.Thistypeofdeviceisavailablewithawidevarietyoffeatures,amongthem,remotetemperaturesensing.Toenableremotesensing,mosthigh-performanceCPUsincludeanon-chiptransistorthatprovidesavoltageanalogofthetemperature.(Onlyoneofthetransistorstwop-njunctionsisused.)Figure3showsaremoteCPUbeingmonitoredusingthistechnique.Otherapplicationsutilizeadiscretetransistortoperformthesamefunction.Figure3.Auser-programmabletemperaturesensormonitorsthetemperatureofaremoteCPUson-chipp-njunction.Anotherimportantfeaturefoundonsomeofthesetypesofsensors(includingthesensorshowninFigure3)istheabilitytointerruptamicrocontrollerwhenthemeasuredtemperaturefallsoutsidearangeboundedbyhighandlowlimits.Onothersensors,aninterruptisgeneratedwhenthemeasuredtemperatureexceedseitherahighoralowtemperaturethreshold(i.e.,notboth).ForthesensorinFigure3,thoselimitsaretransmittedtothetemperaturesensorviatheSMBusinterface.Ifthetemperaturemovesaboveorbelowthecircumscribedrange,thealertsignalinterruptstheprocessor.PicturedinFigure4isasimilardevice.Insteadofmonitoringonep-njunction,however,itmonitorsfourjunctionsanditsowninternaltemperature.BecauseMaximsMAX1668consumesasmallamountofpower,itsinternaltemperatureisclosetotheambienttemperature.Measuringtheambienttemperaturegivesanindicationastowhetherornotthesystemfanisoperatingproperly.Figure4.Auser-programmabletemperaturesensormonitorsitsownlocaltemperatureandthetemperaturesoffourremotep-njunctions.ControllingafanwhilemonitoringremotetemperatureisthechieffunctionoftheICshowninFigure5.Usersofthispartcanchoosebetweentwodifferentmodesoffancontrol.Inthe第4页PWMmode,themicrocontrollercontrolsthefanspeedasafunctionofthemeasuredtemperaturebychangingthedutycycleofthesignalsenttothefan.Thispermitsthepowerconsumptiontobefarlessthanthatofthelinearmodeofcontrolthatthispartalsoprovides.BecausesomefansemitanaudiblesoundatthefrequencyofthePWMsignalcontrollingit,thelinearmodecanbeadvantageous,butatthepriceofhigherpowerconsumptionandadditionalcircuitry.Theaddedpowerconsumptionisasmallfractionofthepowerconsumedbytheentiresystem,though.Figure5.Afancontroller/temperaturesensorICuseseitheraPWM-orlinear-modecontrolscheme.ThisICprovidesthealertsignalthatinterruptsthemicrocontrollerwhenthetemperatureviolatesspecifiedlimits.Asafetyfeatureintheformofthesignalcalledovert(anabbreviatedversionofovertemperature)isalsoprovided.Ifthemicrocontrollerorthesoftwareweretolockupwhiletemperatureisrisingtoadangerouslevel,thealertsignalwouldnolongerbeuseful.However,overt,whichgoesactiveoncethetemperaturerisesabovealevelsetviatheSMBus,istypicallyusedtocontrolcircuitrywithouttheaidofthemicrocontroller.Thus,inthishigh-temperaturescenariowiththemicrocontrollernotfunctioning,overtcouldbeusedtoshutdownthesystempowersuppliesdirectly,withoutthemicrocontroller,andpreventapotentiallycatastrophicfailure.ThisdigitalI/Oclassofdevicesfindswidespreaduseinservers,batterypacks,andhard-diskdrives.Temperatureismonitoredinnumerouslocationstoincreaseaserversreliability:atthemotherboard(whichisessentiallytheambienttemperatureinsidethechassis),insidetheCPUdie,andatotherheat-generatingcomponentssuchasgraphicsacceleratorsandhard-diskdrives.Batterypacksincorporatetemperaturesensorsforsafetyreasonsandtooptimizechargingprofiles,whichmaximizesbatterylife.Therearetwogoodreasonsformonitoringthetemperatureofahard-diskdrive,whichdependsprimarilyonthespeedofthespindlemotorandtheambienttemperature:Thereaderrorsinadriveincreaseattemperatureextremes,andaharddisksMTBFisimprovedsignificantlythroughtemperaturecontrol.Bymeasuringthetemperaturewithinthesystem,youcancontrolmotorspeedtooptimizereliabilityandperformance.Thedrivecanalsobeshutdown.Inhigh-endsystems,alertscanbegeneratedforthesystemadministratortoindicatetemperatureextremesorsituationswheredatalossispossible.Analog-PlusTemperatureSensors第5页Analog-plussensorsaregenerallysuitedtosimplermeasurementapplications.TheseICsgeneratealogicoutputderivedfromthemeasuredtemperatureandaredistinguishedfromdigitalI/Osensorsprimarilybecausetheyoutputdataonasingleline,asopposedtoaserialbus.Inthesimplestinstanceofananalog-plussensor,thelogicoutputtripswhenaspecifictemperatureisexceeded.Someofthesedevicesaretrippedwhentemperaturerisesaboveapresetthreshold,others,whentemperaturedropsbelowathreshold.Someofthesesensorsallowthetemperaturethresholdtobeadjustedwitharesistor,whereasothershavefixedthresholds.ThedevicesshowninFigure6arepurchasedwithaspecificinternaltemperaturethreshold.Thethreecircuitsillustratecommonusesforthistypeofdevice:providingawarning,shuttingdownapieceofequipment,orturningonafan.Figure6.ICsthatsignalwhenatemperaturehasbeenexceededarewellsuitedforover/undertemperaturealarmsandsimpleon/offfancontrol.Whenanactualtemperaturereadingisneeded,andamicrocontrollerisavailable,sensorsthattransmitthereadingonasinglelinecanbeuseful.Withthemicrocontrollersinternalcountermeasuringtime,thesignalsfromthistypeoftemperaturesensorarereadilytransformedtoameasureoftemperature.ThesensorinFigure7outputsasquarewavewhosefrequencyisproportionaltotheambienttemperatureinKelvin.ThedeviceinFigure8issimilar,buttheperiodofthesquarewaveisproportionaltotheambienttemperatureinkelvins.第6页Figure7.AtemperaturesensorthattransmitsasquarewavewhosefrequencyisproportionaltothemeasuredtemperatureinKelvinformspartofaheatercontrollercircuit.Figure8.ThistemperaturesensortransmitsasquarewavewhoseperiodisproportionaltothemeasuredtemperatureinKelvin.Becauseonlyasinglelineisneededtosendtemperatureinformation,justasingleoptoisolatorisrequiredtoisolatethesignalpath.Figure9,atrulynovelapproach,allowsuptoeighttemperaturesensorstobeconnectedonthiscommonline.TheprocessofextractingtemperaturedatafromthesesensorsbeginswhenthemicrocontrollersI/Oportstrobesallthesensorsonthelinesimultaneously.Themicrocontrolleristhenquicklyreconfiguredasaninputinordertoreceivedatafromeachofthesensors.Thedataareencodedastheamountoftimethattranspiresafterthesensorsarestrobed.Eachofthesensorsencodesthistimeafterthestrobepulsewithinaspecificrangeoftime.Collisionsareavoidedbyassigningeachsensoritsownpermissibletimerange.Figure9.Amicrocontrollerstrobesuptoeighttemperaturesensorsconnectedonacommonlineandreceivesthetemperaturedatatransmittedfromeachsensoronthesameline.Theaccuracyachievedbythismethodissurprisinglyhigh:0.8Cistypicalatroomtemperature,preciselymatchingthatoftheICthatencodestemperaturedataintheformofthefrequencyofthetransmittedsquarewave.Thesameistrueofthedevicethatusestheperiodofthesquarewave.Thesedevicesareoutstandinginwire-limitedapplications.Forexample,whenatemperaturesensormustbeisolatedfromthemicrocontroller,costsarekepttoaminimumbecauseonlyoneoptoisolatorisneeded.ThesesensorsarealsoofgreatutilityinautomotiveandHVACapplications,becausetheyreducetheamountofcopperrunningoverdistances.AnticipatedTemperatureSensorDevelopmentsICtemperaturesensorsprovideavariedarrayoffunctionsandinterfaces.Asthesedevicescontinuetoevolve,systemdesignerswillseemoreapplication-specificfeaturesaswellasnew第7页waysofinterfacingthesensorstothesystem.Finally,theabilityofchipdesignerstointegratemoreelectronicsinthesamedieareaensuresthattemperaturesensorswillsoonincludenewfunctionsandspecialinterfaces.中文翻译稿温度传感器芯片简化设计当选择一个温度传感器时，将不再局限于模拟输出或数字输出设备。现在有的传感器类型，会让你有很大的选择空间。在市场上的所有的温度传感器提供模拟输出。热敏电阻、RTDs和热电偶是另一种模拟输出设备，硅温度传感器。在大多数应用程序中，不幸的是，这些模拟输出设备需要比较器、ADC或在他们的输出放大器。因此，当更高的级别，集成的变得可行，数字接口的温度传感器成为可用。这些芯片在多种形式出第8页售，从简单信号在特定温度时的设备已超过那些报告同时提供警告在升温设置的远程和本地的温度。选择现在不是简单地之间模拟输出和数字输出的传感器；有范围广泛的传感器类型可供选择。温度传感器的种类图1。传感器和IC制造商目前提供温度传感器的四的类。在图1中举例说明四种温度传感器类型。一种理想的模拟传感器提供输出电压，这是一个完美的线性温度（A）的功能。在数字I/O类的传感器(B)中，温度多1和0的表单中的数据传递到微控制器，通常是通过串行总线。沿着相同的总线，数据被发送到温度传感器的微控制器，通常设置的警报针的数字输出将旅行的温度限制。警报中断微控制器时已经超过温度限制。这种类型的设备，还可以提供风扇控制。模拟正量传感器(C)被应用在多种类型的数字输出上。当超过特定温度的时候，Vout对温度曲线是一个数字输出。在这种情况下，增加到模拟温度传感器的“正信号”只不过是一个比较器的参考电压。其他的类型“正信号”部分在以频率和方波的形式储存以后被延迟，这些将会在以后讨论。系统监视器（D）是四种类型当中最复杂的集成电路。除了功能由数字I/O类型提供外，当电压上升或下降到通过I/O总线设置的极限的时候这类型装置的监测系统会报警。风扇监控和/或控制包含在这种类型中的集成电路。在某些情况下，此类设备用于决定一个风扇是否正在工作。更多复杂控制风扇如一或更多量过的温度的功能。系统监视器传感器这里不讨论，但简短提到温度传感器的类型。模拟输出温度传感器热电阻和硅温度传感器被广泛地应用在模拟输出温度传感器上。图2清楚地显示当需要时电压和温度的线性关系，硅温度传感器是比热敏电阻好得多。在狭窄的温度范围之内，热敏电阻可以提供合理的线性和良好的敏感特性。许多构成原始电路的热敏电阻已经被硅温度传感器代替。第9页图2。热敏电阻和硅温度传感器这两个模拟输出温度探测器的比较。硅温度传感器有不同的输出刻度和偏移量。例如，与绝对温度成比例的输出转换功能，还有其他与摄氏温度和华氏温度成比例。摄氏温度部分提供一种组合以便温度能被单端补给传感器测试。在大多数应用程序中，这些装置的输出被装入一个比较器或A/D转换器的温度数据转换为数字格式。这些附加的装置，热电阻和硅温度传感器继续被使用是由于在很多情况下它的成本低和使用方便。数字I/O温度传感器大约在五年前，一种新型温度传感器出现了。这种装置包括一个允许与微控制器进行通信的数字接口。接口通常是IC或SMBus的串行总线，但其他的串行接口，如SPI是共用的。除了要报告的微控制器，温度读数，该接口也从微控制器接收指令。这些指令通常温度限制，如果超出，将中断微控制器的温度传感器在集成电路上的数字信号。然后微控制器可以调整风扇速度，或减慢微处理器的速度，例如，保持温度在控制下。这种类型装置有多样性的特点。远程温度传感，为了能够远程测量，大多数的高效处理器提供一个温度的模拟电压芯片晶体。（晶体管的两个p-n结仅被使用）。图3显示了一个使用这种技术检测的处理器。其他应用利用离散的晶体管实现相同的功能。图3。设计的温度传感器可远程测试处理器芯片上的p-n结温度。这种类型的传感器的另一个重要特征是测量温度在高或低极限外有中断微控制器的能力（包括在图3中所示的传感器）。在其他的传感器上，当测量的温度超过极限的时候，它会产生一个高或低的温度门限，对於在图3中的传感器，那些极限经由SMBus接口被传送到温度传感器。如果温度移动到周围画线范围上面或下面，报警信号会中断处理器。在图4中画一种类似的装置。而不是监测一个p-n结温度，它会检测四个结和其内第10页部的温度。因为Maxim的MAX1668消耗很小的能量，它内部的温度接近周围温度。周围温度的测量给出关于系统风扇是否正常工作的指示。图4。温度传感器可检测自己本地的温度和四个远程p-n结的温度。在图5中显示，控制风扇是在远程温度监测时集成电路的主要功能。这一部分的使用能在风扇控制的两种不同的模式之间进行选择。在PWM模式中，微控制器控制风扇转速是通过更改发送到风扇的信号周期测量温度的一种功能。它允许电力消耗远少于该部分的线性模式控制所提供的。因为某些风扇在PWM信号控制它的频率下发出一种听得见的声音，这种线性模式可以是有利的，但是需要较高功率的消耗和附加的电路。额外的功耗是整个系统功耗的一