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TIDAC568716位双通道500MSPS数模转换器参考设计方案关键字：500MSPS数模转换器,DAC5687TI公司的DAC5687一款具有2x、4x和8x插值过滤器、一个复杂的数控振荡器、车载时钟乘法器，IQ补偿和片上参考电压的双通道16位高速数模转换器。这个DAC5687兼容DAC56836芯片，应用时只需要更改寄存器的设置就可以完成，并提供了额外的功能和优越的线性、噪声、串扰和锁相环相位噪声性能。该芯片具有六个信号处理模块：两个插值数字滤波器、一个具有32位数控振荡器的混频器、一个正交调制补偿模块、两个数字滤波器另一个插值模块、fS/2和fS/4的粗混频模块。不同的操作模式下启用或旁路信号处理模块。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。TheDAC5687isadual-channel16-bithigh-speeddigital-to-analogconverter(DAC)withintegrated2×,4×,and8×interpolationfilters,acomplexnumericallycontrolledoscillator(NCO),onboardclockmultiplier,IQcompensation,andon-chipvoltagereference.TheDAC5687ispin-compatibletotheDAC5686,requiringonlychangesinregistersettingsformostapplications,andoffersadditionalfeaturesandsuperiorlinearity,noise,crosstalk,andPLLphasenoiseperformance.TheDAC5687hassixsignalprocessingblocks:twointerpolate-by-twodigitalfilters,afinefrequencymixerwith32-bitNCO,aquadraturemodulationcompensationblock,anotherinterpolate-by-twodigitalfilter,andacoarsefrequencymixerwithfS/2orfS/4.Thedifferentmodesofoperationenableorbypassthesignalprocessingblocks.Thecoarseandfinemixerscanbecombinedtospanawiderrangeoffrequencieswithfineresolution.TheDAC5687allowsbothcomplexorrealoutput.CombiningthefrequencyupconversionandcomplexoutputproducesaHilberttransformpairthatisoutputfromthetwoDACs.AnexternalRFquadraturemodulatorthenperformsthefinalsingle-sidebandupconversion.TheIQcompensationfeatureallowsoptimizationofphase,gain,andoffsettomaximizesidebandrejectionandminimizeLOfeedthroughforananalogquadraturemodulator.TheDAC5687includesseveralinputoptions:single-portinterleaveddata,evenandoddmultiplexingathalf-rate,andaninputFIFOwitheitherexternalorinternalclocktoeasetheinputtimingambiguitywhentheDAC5687isclockedattheDACoutputsamplerate.DAC5687主要特性：500MSPSSelectable2×-8×InterpolationOn-ChipPLL/VCOClockMultiplierFullIQCompensationIncludingOffset,Gain,andPhaseFlexibleInputOptions:FIFOWithLatchonExternalorInternalClockEven/OddMultiplexedInputSinglePortDemultiplexedInputComplexMixerWith32-BitNCOFixedFrequencyMixerWithfS/4andfS/21.8-Vor3.3-VI/OVoltageOn-Chip1.2-VReferenceDifferentialScalableOutput:2mAto20mAPinCompatibletoDAC5686HighPerformance81-dBcACLRWCDMATM1at30.72MHz72-dBcACLRWCDMATM1at153.6MHzPackage:100-PinHTQFPAPPLICATIONSCellularBaseTransceiverStationTransmitChannelCDMA:W-CDMA,CDMA2000,TD-SCDMATDMA:GSM,IS-136,EDGE/UWC-136OFDM:802.16CableModemTerminationSystemDAC5687应用：TETRABaseStationTV:High-Definition(HDTV)WirelessInfrastructure:HeterodyneRX/TXWirelessInfrastructure:Hi-PerfWiMAX802.16,2.5-3.5GHzBTSRX/TX图1.DAC5687内部方框图DAC5687方案介绍：TheDAC5687EVMprovidesaplatformforevaluatingtheDAC5687digital-to-analogconverter(DAC)undervarioussignal,reference,andsupplyconditions.ThisdocumentshouldbeusedincombinationwiththeEVMschematicdiagramsupplied.EVMBasicFunctionsDigitalinputstotheDACcanbeprovidedwithCMOSlevelsignalsupto250MSPS(externalclockmode)throughtwo34-pinheaders.Thisenablestheusertoprovidehigh-speeddigitaldatatotheDAC5687device.TheanalogoutputsfromtheDACareavailableviaSMAconnectors.BecauseofitsflexibledesigntheanalogoutputsoftheDAC5687devicecanbeconfiguredtodrivea50-Ωterminatedcableusinga4:1or1:1impedanceratiotransformer,orsingle-endedreferredtoAVDD.TheEVMalsoallowsforanoptiontodoubletheoutputpowerbysummingtheDACAandDACBoutputsthrougha1:1transformer.TheEVMallowstheusertoinputsingle-ended,TTL/CMOSlevelsignals,togeneratedifferentialclocksourcesforbothCLK1andCLK2.InputClocks,forproperconfigurationandoperation.PowerconnectionstotheEVMareviabananajacksockets.InadditiontotheinternalbandgapreferenceprovidedbytheDAC5687device,optionsontheEVMallowanexternalreferencetobeprovidedtotheDAC.TheDAC5687EVMallowstheusertoprogramtheDAC5687internalregisterswiththesuppliedcomputerparallelportcableandserialinterfacesoftware.TheinterfaceallowsreadandwriteaccesstoallregistersthatdefinetheoperationmodeoftheDAC5687device.DAC5687方案原理图：图2.DAC5687方案原理图DAC5687方案材料清单：PCB元件布局图：AO-Electronics傲壹电子官网：中文网：