外文翻譯--半導體.doc

Abstract:ONSemiconductor(OnSemi)CompanyA-B-typemainNCP2890audiopoweramplifierperformancecharacteristicsandthebasicworkingprinciple,givethedesignoftheNCP2890audioamplifierwithatypicalapplicationcircuitanddesignmethod.Keywords:NCP2890；ABtype；audioamplifier1outlinesONSemiconductorNCP2890are(OnSemi)hasintroducedcost-effective,full-featuredaudioSeriesProductsofthefirstaudiopoweramplifier,itisdesignedformobilephoneandPDA,suchasbattery-poweredwirelessdevicesdesignedforproduction,areonekindsofverygoodqualitywirelessapplicationsA-B-typeaudiopoweramplifiercanprovidecustomerswithsuperioraudioperformance.Thedevicehasasuperiorpowersupplyrejectionratio(PSRR)andtotalharmonicdistortionplusnoise(THD+N)characteristicsatthesametime,acombinationofexternalcontrolgaincharacteristicsandadjustablebootandshutdowntimedelayfunction,andhaveastartupandshutdowncontrolcircuitthatcaneliminatetheopeningandclosingofsuchaudiopoweramplifiergeneratedaudiblenoise,canbeflexiblyusedinportableaudioequipmentdesign.NCP2890allowslithium-ionorlithiumpolymerbatterydirectpowersupply,andthusobviatestheextraLowDropoutRegulators(LDO),whilereducingboardspaceandreducestheoverallcost.2-chipstructureandperformanceparametersTomeetthespecificneedsofthemarket,NCP2890currentlyhaveMi-crobump-9(2.25mm2)andMicro-8(14.7mm2)twodifferentkindsofpackagingforms,showninFigure1withitspindiagram,allcitedthefunctionofthefootsuchasTable1NCP2890include671internaltransistor,MOSgate1899,whichhasexcellentaudioperformance,Table2givetheNCP2890themainperformanceparameters.Table2NC2890mainperformanceparameters3ApplicationCircuitDesignFigure2showsatypicalNCP2890audioamplifierapplicationcircuit,Figure2canbeseenfrom,NCP2890externalonlyusedtoadjustthegainofthetworesistors,aninputcouplingcapacitor,abypasscapacitor,suchasasmallnumberofcomponents,thereforetheexternalrequirementsdevicesextremelyeasy3.1WorkingPrinciplecircuitNCP2890containstwoidenticalpoweramplifiers,theinputaudiosignalbythefirstpoweramplifieramplifiedtheoutputfromtheOUTA.VoltagegainbyexternalresistorRfandRintheratioofthedecision.TheaudiosignalamplifiedbythegainofoneandthenthesecondpoweramplifierRPenlarge,andOUTBoutput.BecauseofOUTAandOUTBclient-sideaudiooutputsignalpowerequaltothesize,phasecontrast,andtwooutputs(OUTAandOUTB)DCthesamestaticpotential(Vp/2),so,speakerscanbeconnecteddirectlytotheclientOUTAandOUTB,ratherthanincreasetheoutputcouplingcircuit.TwopoweramplifieroutputstageusingPMOSandNMOStransistorsbythespecialdesign.Normalconduction,thechannelresistanceoflessthan0.6,andthusitsoutputwaveformdistortionisverysmall.Generalpoweramplifierintheopenandturnofftheprocesswillproducethehumanearcanhearthenoise,inordertoeliminateaudiblenoise,in-housedesignedNCP2890noiseeliminationcircuit.Boottime,addtheswitchcontrollogichighendofbypasscapacitorCbyontheDCvoltagevaluesbegintoincreaseexponentiallywhenthevoltagevaluereachesthevalueofcommon-modevoltage(Vp/2)whenthebeginningofoutputpower(thisprocessaround50ms)；andshutdown,thecontrollow-leveltermination,loadtobeconnectedtothegroundingterminal,theoutputpowertozero,whentheDCcircuitquiescentcurrentlessthan100nA3.2circuitelementparametersRinandRfamplifierusedtosettheclosed-loopgain,NCP2890inordertooptimizetheperformanceoftheclosed-loopgainamplifiershouldbesetatarelativelylowlevel,THDatthistimethesmallest,thelargestsignaltonoiseratio,widefrequencyresponserange.Soinmostcases,theclosed-loopgainamplifierinstalledingeneralbetween25,therefore,inputresistance(Rin)valuesofDinthe20kmoreappropriate,andRfisusedtoadjusttheclosed-loopgaintocontroltheoutputpower.InputcouplingcapacitorCininputamplifierusedtoisolatetheDCvoltage,Rinsimultaneouslywiththeformationofahigh-passfilter,butitwillaffectthefiltercutofffrequencythreshold.Inordertoenablethelow-frequencysignalsdonotdecaytoogreat,intheory,Cinshouldtakealargervalue,whilethelargercapacitorchargeanddischargetimeislong,therefore,requiredalongerperiodoftimetomakeinputtoreachthestaticpotentialVp/2,whichiseasytomaketheoutputnoisegeneratedboot.Therefore,inmostcases,Cinvaluesgenerallybetween0.10.39Fmoreappropriate(Rin=20kpm).BypasscapacitorCbyarecommon-modevoltage(Vp/2)ofthefilter,istodeterminethelengthoftheboot,bootnoisereductionasakeycomponent,inmostcases,1.0FbypasscapacitorCbycheckmoreappropriate.R1andR2componentsofthepartialpressurecircuitchipsusedtoproducethestartvoltage,generalR1value100k,designedaccordingtovoltagevaluetoselecttheresistanceR2,aslongasthepressuresothatthevalueisgreaterthan1.2Vcanbeabout3.3CautionWhenthecircuitreachesthemaximumoutputpowerPorms=1.0W,Vp=5.0V,RL=8.0whentheloadonthepeakcurrentof500mA.Inordertopreventtheoutputloadcircuitwhentheoutputcurrentistoolarge,setupchipoutputcurrentdetectioncircuit,itcanbelimitedtoamaximumoutputcircuit800mA.Inthisway,oncetheoutputcurrentofover800mA,theoutputsideofthefourMOStransistorswillbegatedoffandnolongervoltageoutputcurrent.Whenthechiptemperatureexceeds160,theinternalamplifierwillbeshutdownandstopworkinguntilthetemperatureisbelow140,theinternalamplifiertobeginworktorestart.DespitetheNCP2890containsaninternalover-currentandover-temperatureprotectioncircuit,butwheninuse,wemustpayattentiontopowersupplyvoltageshouldnotexceedtheirlimits,soastoavoidchipdamage.摘要：介紹了安森美半導體(OnSemi)公司類音頻功率放大器NCP2890的主要性能特點和基本工作原理，給出了用NCP2890設計音頻功放的典型應用電路和設計方法。關鍵詞：NCP2890；A-B類；音頻放大器1概述是安森美半導體()公司推出的經(jīng)濟高效、功能齊備的音頻系列產(chǎn)品中的第一款音頻功率放大器，它是專為手機和等電池供電的無線設備而設計生產(chǎn)的，是一種質量非常優(yōu)秀的無線應用類音頻功率放大器，可為客戶提供卓越的音頻性能。該器件在具有出眾的電源抑制比()和總諧波失真加噪聲()特性的同時，綜合了外部控制增益特征和可調(diào)式開機與關機延時功能，并具有“開機和關機”控制電路，能消除開啟和關閉此類音頻功率放大器時產(chǎn)生的可聽噪聲，可靈活應用于便攜式音頻設備的設計中。允許鋰離子或鋰聚合物電池直接供電，因而省卻了額外的低壓降穩(wěn)壓器()，同時減少了電路板的占用空間并降低了整體成本.2芯片結構與性能參數(shù)為滿足特定市場的需求，目前有-()和()兩種不同的封裝形式，圖所示為其引腳排列圖，各引腳的功能如表列.內(nèi)部包括個晶體管、個門電路，因而具有極佳的音頻性能，表給出了的主要性能參數(shù).應用電路設計圖所示為音頻功放的典型應用電路，由圖可見，外圍只有用來調(diào)節(jié)增益的兩個電阻、一個輸入耦合電容、一個旁路電容等少數(shù)幾個元件，因此所需外圍器件極其簡單電路工作原理內(nèi)含兩個完全一樣的功率放大器，輸入的音頻信號經(jīng)第一個功率放大器放大后從輸出。電壓增益由外接電阻與的比值決定。放大后的音頻信號再經(jīng)增益為的第二個功率放大器進行反相放大，并從輸出。由于端與端輸出的音頻功率信號大小相等、相位相反，且兩個輸出端(和)的直流靜態(tài)電位相同（），所以，揚聲器可以直接連接到與端，而不用增加輸出耦合電路。兩個功率放大器的輸出級均采用和晶體管特殊設計而成。正常導通時，其溝道電阻小于，因而其輸出波形失真非常小.一般的功率放大器在開啟和關閉過程中會產(chǎn)生人耳可聽到的噪聲，為了消除這種可聽噪聲，在內(nèi)部專門設計了消噪聲電路。開機時，邏輯高電平加到開關控制端，旁路電容上的直流電壓值開始按指數(shù)規(guī)律增加，當電壓值達到共模電壓值（）時，開