外文翻译--半导体.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：介绍了安森美半导体(OnSemi)公司类音频功率放大器NCP2890的主要性能特点和基本工作原理，给出了用NCP2890设计音频功放的典型应用电路和设计方法。关键词：NCP2890；A-B类；音频放大器1概述是安森美半导体()公司推出的经济高效、功能齐备的音频系列产品中的第一款音频功率放大器，它是专为手机和等电池供电的无线设备而设计生产的，是一种质量非常优秀的无线应用类音频功率放大器，可为客户提供卓越的音频性能。该器件在具有出众的电源抑制比()和总谐波失真加噪声()特性的同时，综合了外部控制增益特征和可调式开机与关机延时功能，并具有“开机和关机”控制电路，能消除开启和关闭此类音频功率放大器时产生的可听噪声，可灵活应用于便携式音频设备的设计中。允许锂离子或锂聚合物电池直接供电，因而省却了额外的低压降稳压器()，同时减少了电路板的占用空间并降低了整体成本.2芯片结构与性能参数为满足特定市场的需求，目前有-()和()两种不同的封装形式，图所示为其引脚排列图，各引脚的功能如表列.内部包括个晶体管、个门电路，因而具有极佳的音频性能，表给出了的主要性能参数.应用电路设计图所示为音频功放的典型应用电路，由图可见，外围只有用来调节增益的两个电阻、一个输入耦合电容、一个旁路电容等少数几个元件，因此所需外围器件极其简单电路工作原理内含两个完全一样的功率放大器，输入的音频信号经第一个功率放大器放大后从输出。电压增益由外接电阻与的比值决定。放大后的音频信号再经增益为的第二个功率放大器进行反相放大，并从输出。由于端与端输出的音频功率信号大小相等、相位相反，且两个输出端(和)的直流静态电位相同（），所以，扬声器可以直接连接到与端，而不用增加输出耦合电路。两个功率放大器的输出级均采用和晶体管特殊设计而成。正常导通时，其沟道电阻小于，因而其输出波形失真非常小.一般的功率放大器在开启和关闭过程中会产生人耳可听到的噪声，为了消除这种可听噪声，在内部专门设计了消噪声电路。开机时，逻辑高电平加到开关控制端，旁路电容上的直流电压值开始按指数规律增加，当电压值达到共模电压值（）时，开