基于嵌入式处理器的vlsi芯片的温度自动控制英文翻译大学本科毕业论文.docx

基于嵌入式处理器的vlsi芯片的温度自动控制英文翻译大学本科毕业论文.docx

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基于嵌入式处理器的vlsi芯片的温度自动控制英文翻译大学本科毕业论文

EmbeddedProcessorBasedAutomaticTemperatureControlofVLSIChips

Abstract

ThispaperpresentsembeddedprocessorbasedautomatictemperaturecontrolofVLSIchips,usingtemperaturesensorLM35andARMprocessorLPC2378.Duetotheveryhighpackingdensity,VLSIchipsgetheatedverysoonandifnotcooledproperly,theperformanceisverymuchaffected.Inthepresentwork,thesensorwhichiskeptverynearproximitytotheICwillsensethetemperatureandthespeedofthefanarrangedneartotheICiscontrolledbasedonthePWMsignalgeneratedbytheARMprocessor.Abuzzerisalsoprovidedwiththehardware,toindicateeitherthefailureofthefanoroverheatingoftheIC.TheentireprocessisachievedbydevelopingasuitableembeddedCprogram.

Keywords:

Temperaturesensor,ARMprocessor,VLSIchips,BrushlessDCmotor

1.Introduction

WiththephenomenaldevelopmentsinVLSItechnology,theambitiousICdesignersaretryingtoputmoretransistorsintosmallerpackages.So,theICsrunathigherspeedsandproducelargeamountofheatwhichcreatestheproblemofthermalmanagement.Forexample,nowadaystheCPUchipsarebecomingsmallerandsmallerwithalmostnoroomfortheheattoescape.Thetotalpowerdissipationlevelsnowresideontheorderof100Wwithapeakpowerdensityof400-500W/Cm2,andarestillsteadilyclimbing.

Asthechiptemperatureincreasesitsperformanceisverymuchdegradedbyparametersshift,decreaseinoperatingfrequenciesandout-ofspecificationoftimings.Sothehighspeedchipsmustbecooledtomaintaingoodperformanceforthelongestpossibleoperatingtimeandoverthewidestpossiblerangeofenvironmentalconditions.Themaximumallowabletemperatureforahighspeedchiptomeetitsparametricspecificationsdependsontheprocessandhowthechipisdesigned.

Amongthevariouscoolingtechniques,heatsinks,heatpipes,fansandclockthrottlingareusuallyemployed.Amongthesetechniques,fanscandramaticallyreducethetemperatureofahighspeedchip,buttheyalsogenerateagreatdealofacousticnoise.Thisnoisecanbereducedsignificantlybyvarying,thefansspeedbasedontemperaturei.e.thefancanturnslowlywhenthetemperatureislowandcanspeedupasthetemperatureincreases.Theotherprominentmethodisclockthrottlingi.e.reducingtheclockspeedtoreducepowerdissipation.Butitalsoreducesthesystemperformanceandthesystemsfunctionalityislost.So,theobjectiveofthepresentworkis,todesignahardwaresystemconsistingofabrushlessDCmotorfanwhosespeediscontrolledbasedonthetemperatureofthechip,sensedbythesensorLM35.TheLM35seriesareprecisionintegrated-circuittemperaturesensors,whoseoutputvoltageislinearlyproportionaltotheCelsius（Centigrade）temperature.TheLM35thushasanadvantageoverlineartemperaturesensorscalibratedinKelvin,astheuserisnotrequiredtosubtractalargeconstantvoltagefromitsoutputtoobtainconvenientCentigradescaling.TheLM35doesnotrequireanyexternalcalibrationortrimmingtoprovidetypicalaccuraciesof±1⁄4°Catroomtemperatureand±3⁄4°Coverafull−55to+150°Ctemperaturerange.Lowcostisassuredbytrimmingandcalibrationatthewaferlevel.TheLM35’slowoutputimpedance,linearoutput,andpreciseinherentcalibrationmakeinterfacingtoreadoutorcontrolcircuitryespeciallyeasy.Itcanbeusedwithsinglepowersupplies,orwithplusandminussupplies.Asitdrawsonly60μAfromitssupply,ithasverylowselfheating,lessthan0.1°Cinstillair.TheLM35isratedtooperateovera−55°to+150°Ctemperaturerange,whiletheLM35Cisratedfora−40°to+110°Crange（−10°withimprovedaccuracy）.TheLM35seriesisavailablepackagedinhermeticTO-46transistorpackages,whiletheLM35C,LM35CA,andLM35DarealsoavailableintheplasticTO-92transistorpackage.TheLM35Disalsoavailableinan8-leadsurfacemountsmalloutlinepackageandaplasticTO-220package.TomonitorthevoltageattheterminalsoftheDCmotorfan,thePWMsignalisgeneratedbytheARM7TDMIprocessor.ThisPWMsignalischangedinaccordancetotheoutputoftheLM35temperaturesensor.Sotheimportantcomponentofthisentireprojectisthetemperaturesensor.

2.Description

InARMprocessorbasedautomatictemperaturecontrolsystem,theoutputofthetemperaturesensorisfedtotheonchipADCandtheoutputoftheADCisgiventotheL293DdriverICwhichinturnisfedtoDCmotorfanasshownintheblockdiagraminFig.1.AgraphicLCD（128x64pixels）isinterfacedtotheARMLPC2378processortodisplaythetemperatureoftheICandthespeedofthefan.Abuzzerisalsoconnectedtotheprocessorwhichgivesanindication,incaseofthefailureofthefanoroverheatingofthechipbeyondsomelevel.TheentirecircuitdiagramisshowninFig.2.

Fig.1.Blockdiagram.

Fig.2.CircuitDiagram.

3.SoftwareDescription

ThepresentworkisimplementedusingARMIARWorkbenchIDEandthenecessaryembeddedCprogramisdevelopedanddumpedintotheembeddedprocessorusingFlashmagicISPUtility.TheARMIARWorkbenchIDEisaverypowerfulIntegratedDevelopmentEnvironment（IDE）thatallowsyoutodevelopandmanagecompleteembeddedapplicationprojects.In-SystemProgrammingisprogrammingorreprogrammingtheon-chipflashmemory,usingtheboot-loadersoftwareandaserialport.TheLPC2387microcontrollerisbasedona16-bit/32-bitARM7TDMI-SCPUwithreal-timeemulationthatcombinesthemicrocontrollerwith512kBofembeddedhigh-speedflashmemory.

A128-bitwidememoryinterfaceanduniqueacceleratorarchitectureenable32-bitcodeexecutionatthemaximumclockrate.ForcriticalperformanceininterruptserviceroutinesandDSPalgorithms,thisincreasesperformanceupto30%overThumbmode.Forcriticalcodesizeapplications,thealternative16-bitThumbmodereducescodebymorethan30%withminimalperformancepenalty.TheLPC2387isidealformulti-purposeserialcommunicationapplications.Itincorporatesa10/100EthernetMediaAccessController（MAC）,USBfullspeeddevicewith4kBofendpointRAM,fourUARTs,twoCANchannels,anSPIinterface,twoSynchronousSerialPorts（SSP）,threeI2Cinterfaces,andanI2Sinterface.Thisblendofserialcommunicationsinterfacescombinedwithanon-chip4MHzinternaloscillator,64kBSRAM,16kBSRAMforEthernet,16kBSRAMforUSBandgeneralpurposeuse,togetherwith2kBbatterypoweredSRAMmakesthisdeviceverywellsuitedforcommunicationgatewaysandprotocolconverters.Various32-bittimers,animproved10-bitADC,10-bitDAC,onePWMunit,aCANcontrolunit,andupto70fastGPIOlineswithupto12edgeorlevelsensitiveexternalinterruptpinsmakethismicrocontrollerparticularlysuitableforindustrialcontrolandmedicalsystems.

TheLPC2378Microcontrollerprovideson-chipboot-loadersoftwarethatallowsprogrammingoftheinternalflashmemoryovertheserialchannel.PhilipsprovidesautilityprogramforIn-SystemprogrammingcalledFlashmagicSoftware.

4.ResultsandConclusions

EmbeddedARMprocessorbasedautomaticspeedcontrolDCmotorfanisdesignedandimplemented.Totestthevalidityofthedesign,thetemperaturesensoriskeptinsideasmallovenanditstemperatureisincreasedbeyondtheroomtemperature.Nowthefanisoperatedtorunwithfullspeedandthetemperatureisfoundtocomebacktonormaltemperature.ThisisrepeatedwithvariousVLSIchipslikePentiumprocessor,FPGAchipsetc.NowthetemperaturesensoriskeptveryneartothePentiumprocessorofthecomputeranditisobservedthat,asthetimelapsesthespeedofthefanisautomaticallyincreasedandthetemperatureofthechipisfoundtobecontrolled.TheseresultsaredisplayedonLCDpanel.Thoughthepresentsystemisworkingwellinthegivenenvironment,stillitisworthwhiletohighlightthefollowingconclusions.

Normally,controllingfanspeedorclockthrottlingbasedontemperaturerequiresthatthetemperatureofthehighspeedchipshouldbefirstmeasured.Thisisdonebyplacingatemperaturesensorclosetothetargetchipeitherdirectlynexttoitorinsomecases,underitorontheheatsink.Thetemperaturemeasuredinthiswaycorrespondstothatofthehighspeedchip,butcanbesignificantlylowerandthedifferencebetweenmeasuredtemperatureandtheactualdietemperatureincreasesasthepowerdissipationincreases.So,thetemperatureofthecircuitboardorheatsinkmustbecorrelatedtothedietemperatureofthehighspeedchip.Ofcourseabetteralternativeispossiblewithanumberofhighspeedchips.ManyCPUs,FPGAsandotherhighspeedICsincludeathermaldiodewhichisactuallyadiodeconnectedbipolartransistor,onthedie.Usingaremotediodetemperaturesensorconnectedtothisthermaldiode,thetemperatureofthehighspeedIC’sdiecanbemeasureddirectlywithanexcellentaccuracy.ThisnotonlyeliminatesthelargetemperaturegradientsinvolvedinmeasuringtemperatureoutsidethetargetIC’spackage,butitalsoeliminatesthelongthermaltimeconstants,fromseveralsecondstominutes,thatcausedelaysinrespondingtodietemperaturechanges.

Thereisalsoadrawbackinfanspeedcontrol.Normallythefanspeediscontrolledbyadjustingthepowersupplyvoltageofthefan.Thisisdonebyalow-frequencyPWMsignal,usuallyintherangeofabout50Hz,whosedutycycleisvariedtoadjustthefan’sspeed.Thisisinexpensiveandalsoefficient.Butthedisadvantageofthismethodisthatitmakesthefansomewhatnosierbecauseofthepulsednatureofthepowersupply.ThePWMwaveformsfastedgescausethefansmechanicalstructuretomove,whichiseasilyaudible.

Insomesystems,itisal