How-to-read-datasheet(译)

HowtoReadaDatasheetPreparedfortheWIMSoutreachprogram5/6/02,D.GroverInordertouseaPICmicrocontroller,aflip-flop,aphotodetector,orpracticallyanyelectronicdevice,youneedtoconsultadatasheet.Thisisthedocumentthatthemanufacturerprovidestellingyou•thetypicaldeviceperformance•minimumandmaximumrequirementsandcharacteristics•whatyoucandotothedevicewithoutharmingit•suggestedusesandhintsManufacturerswantyou,thedesigner,tohaveasuccessfulexperiencewiththeirdevice.Theyaretryingtobehelpful.Theydon’talwayssucceed.Thedatasheetonthefollowingpagesisarelativelygooddatasheet.Ittriestoconciselytellyoueverythingyouneedtoknowaboutthedevice,acommon555timerchip(theduct-tapeoftheelectronicshobbyist).MostdatasheetsforICsfollowthesamegenerallayout.Youdon’thavetounderstandeverythinginadatasheet.There’salotofinformationthatmightnotbeofanyusetoyou.Theannotationsthatfollowtrytopointoutpartsofthedatasheetthatyoushouldpayparticularattentionto.Wheredoyoufinddatasheets?Nowadaysyoucanfindalmostanydatasheetontheinternet,ofteninPDF(Acrobat)form.Forexample,theLM555datasheetfromNationalSemiconductorisontheirwebsiteat(SeeforexampletheCD4538timerchip.)LM555TimerGeneralDescriptionTheLM555isahighlystabledeviceforgeneratingaccuratetimedelaysoroscillation.Additionalterminalsareprovidedfortriggeringorresettingifdesired.Inthetimedelaymodeofoperation,thetimeispreciselycontrolledbyoneexternalre-sistorandcapacitor.Forastableoperationasanoscillator,thefreerunningfrequencyanddutycycleareaccuratelycontrolledwithtwoexternalresistorsandonecapacitor.Thecircuitmaybetriggeredandresetonfallingwaveforms,andtheoutputcircuitcansourceorsinkupto200mAordriveTTLcircuits.FeaturesnDirectreplacementforSE555/NE555nTimingfrommicrosecondsthroughhoursnOperatesinbothastableandmonostablemodesnAdjustabledutycyclenOutputcansourceorsink200mAnOutputandsupplyTTLcompatiblenTemperaturestabilitybetterthan0.005%per˚CnNormallyonandnormallyoffoutputnAvailablein8-pinMSOPpackageApplicationsnPrecisiontimingnPulsegenerationnSequentialtimingnTimedelaygenerationnPulsewidthmodulationnPulsepositionmodulationnLinearrampgeneratorSchematicDiagramDS007851-1February2000LM555Timer©2000NationalSemiconductorCorporationDS007851(Note2)IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.SupplyVoltage+18VPowerDissipation(Note3)LM555CM,LM555CN1180mWLM555CMM613mWOperatingTemperatureRangesLM555C0˚Cto+70˚CStorageTemperatureRange−65˚Cto+150˚CSolderingInformationDual-In-LinePackageSoldering(10Seconds)260˚CSmallOutlinePackages(SOICandMSOP)VaporPhase(60Seconds)215˚CInfrared(15Seconds)220˚CSeeAN-450“SurfaceMountingMethodsandTheirEffectonProductReliability”forothermethodsofsolderingsurfacemountdevices.ElectricalCharacteristics(Notes1,2)(TA=25˚C,VCC=+5Vto+15V,unlessothewisespecified)ParameterConditionsLimitsUnitsLM555CMinTypMaxSupplyVoltage4.516VSupplyCurrentVCC=5V,RL=∞VCC=15V,RL=∞(LowState)(Note4)310615mATimingError,MonostableInitialAccuracy1%DriftwithTemperatureRA=1kto100kΩ,50ppm/˚CC=0.1μF,(Note5)AccuracyoverTemperature1.5%DriftwithSupply0.1%/VTimingError,AstableInitialAccuracy2.25%DriftwithTemperatureRA,RB=1kto100kΩ,150ppm/˚CC=0.1μF,(Note5)AccuracyoverTemperature3.0%DriftwithSupply0.30%/VThresholdVoltage0.667xVCCTriggerVoltageVCC=15V5VVCC=5V1.67VTriggerCurrent0.50.9μAResetVoltage0.40.51VResetCurrent0.10.4mAThresholdCurrent(Note6)0.10.25μAControlVoltageLevelVCC=15VVCC=5V92.6103.33114VPin7LeakageOutputHigh1100nAPin7Sat(Note7)OutputLowVCC=15V,I7=15mA180mVOutputLowVCC=4.5V,I7=4.5mA80200mVLM555(Notes1,2)(Continued)(TA=25˚C,VCC=+5Vto+15V,unlessothewisespecified)ParameterConditionsLimitsUnitsLM555CMinTypMaxOutputVoltageDrop(Low)VCC=15VISINK=10mA0.10.25VISINK=50mA0.40.75VISINK=100mA22.5VISINK=200mA2.5VVCC=5VISINK=8mAVISINK=5mA0.250.35VOutputVoltageDrop(High)ISOURCE=200mA,VCC=15V12.5VISOURCE=100mA,VCC=15V12.7513.3VVCC=5V2.753.3VRiseTimeofOutput100nsFallTimeofOutput100nsNote1:Allvoltagesaremeasuredwithrespecttothegroundpin,unlessotherwisespecified.Note2:AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsi