基于调制解调器参考设计方案.doc

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1、基于调制解调器参考设计方案OnSemiA5191HRT－DHART设计方案OnSemi公司的A5191HRT-D是一款应用于现场仪表及控制的HART单芯片CMOS调制解调器芯片，该芯片具有通过外围器件少数被动器件就可以满足HART物理层的设计需要，可以实现调制、解调、接收滤波、载波监测和输出信号整形等功能。本芯片采用半双功通信模式，为节省电能，在发送信号时，接收电路部分关闭，反之亦然。本文首先介绍芯片的简介、特性、内部框图及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。TheA5191HR

2、Tisasingle−chip,CMOSmodemforuseinhighwayaddressableremotetransducer(HART)fieldinstrumentsandmasters.ThemodemandafewexternalpassivecomponentsprovideallofthefunctionsneededtosatisfyHARTphysicallayerrequirementsincludingmodulation,demodulation,receivefiltering,ca

3、rrierdetect,andtransmit−signalshaping.TheA5191HRTusesphasecontinuousfrequencyshiftkeying(FSK)at1200bitspersecond.Toconservepowerthereceivecircuitsaredisabledduringtransmitoperationsandviceversa.Thisprovidesthehalf−duplexoperationusedinHARTcommunications.A5191H

4、RT主要特性：•Single−chip,Half−duplex1200BitsperSecondFSKModem•Bell202ShiftFrequenciesof1200Hzand2200Hz•3.0V−5.5VPowerSupply•Transmit−signalWaveShaping•ReceiveBand−passFilter•LowPower:OptimalforIntrinsicallySafeApplications•Compatiblewith3.3Vor5VMicrocontroller•Inte

5、rnalOscillatorRequires460.8kHzCrystalorCeramicResonator•MeetsHARTPhysicalLayerRequirements•IndustrialTemperatureRangeof−40°Cto+85°C•Availablein28−pinPLCC,32−pinQFNand32−pinLQFPPackages•ThesearePb−FreeDevicesA5191HRT应用：•HARTMultiplexers•HARTModemInterfaces•4−20

6、mALoopPoweredTransmitters图1.A5191HRT内部方框图A5191HRT方案介绍：TheA5191HRTNGEVBevaluationboardincludesallexternalcomponentsneededforoperatingtheA5191HRTICanddemonstratesthesmallPCBsurfaceareasuchanimplementationrequires.TheEVBallowseasydesignofHARTimplementationsusingA

7、5191HRT.A5191HRT方案原理图：图2.A5191HRT方案原理图A5191HRT方案材料清单：PCB元件布局图：