NXP-PCA9685-16路12位LED驱动控制方案

NXPPCA968516路12位LED驱动控制方案关键词：消费类电子,LED驱动器,PWM,I2CNXP公司的PCA9685是16路12位PWM不是Fm+I2C总线LED控制器,每个LED输出有它独立的12位分辨率(4096步)固定频率PWM控制器,工作频率从40Hz到1000Hz,占空比从0%到100%.工作电压2.3V到5.5V,主要用在RGB或RGBALED驱动器,LED状态显示器,LED显示器,LCD背光和手机或手持设备的键盘背光.本文介绍了PCA9685主要特性和优势,方框图以及典型应用电路图和LCD背光应用电路图.PCA9685:16-channel,12-bitPWMFm+I2C-busLEDcontrollerThePCA9685isanI2C-buscontrolled16-channelLEDcontrolleroptimizedforLCDRed/Green/Blue/Amber(RGBA)colorbacklightingapplications.EachLEDoutputhasitsown12-bitresolution(4096steps)fixedfrequencyindividualPWMcontrollerthatoperatesataprogrammablefrequencyfromatypicalof40Hzto1000Hzwithadutycyclethatisadjustablefrom0%to100%toallowtheLEDtobesettoaspecificbrightnessvalue.AlloutputsaresettothesamePWMfrequency.EachLEDoutputcanbeofforon(noPWMcontrol),orsetatitsindividualPWMcontrollervalue.TheLEDoutputdriverisprogrammedtobeeitheropen-drainwitha25mAcurrentsinkcapabilityat5Vortotempolewitha25mAsink,10mAsourcecapabilityat5V.ThePCA9685operateswithasupplyvoltagerangeof2.3Vto5.5Vandtheinputsandoutputsare5.5Vtolerant.LEDscanbedirectlyconnectedtotheLEDoutput(upto25mA,5.5V)orcontrolledwithexternaldriversandaminimumamountofdiscretecomponentsforlargercurrentorhighervoltageLEDs.ThePCA9685isinthenewFast-modePlus(Fm+)family.Fm+devicesofferhigherfrequency(upto1MHz)andmoredenselypopulatedbusoperation(upto4000pF).AlthoughthePCA9635andPCA9685havemanysimilarfeatures,thePCA9685hassomeuniquefeaturesthatmakeitmoresuitableforapplicationssuchasLCDbacklightingandAmbilight:•ThePCA9685allowsstaggeredLEDoutputonandofftimestominimizecurrentsurges.Theonandofftimedelayisindependentlyprogrammableforeachofthe16channels.ThisfeatureisnotavailableinPCA9635.•ThePCA9685has4096steps(12-bitPWM)ofindividualLEDbrightnesscontrol.ThePCA9635hasonly256steps(8-bitPWM).•WhenmultipleLEDcontrollersareincorporatedinasystem,thePWMpulsewidthsbetweenmultipledevicesmaydifferifPCA9635sareused.ThePCA9685hasaprogrammableprescalertoadjustthePWMpulsewidthsofmultipledevices.•ThePCA9685hasanexternalclockinputpinthatwillacceptuser-suppliedclock(50MHzmax.)inplaceoftheinternal25MHzoscillator.Thisfeatureallowssynchronizationofmultipledevices.ThePCA9635doesnothaveexternalclockinputfeature.•LikethePCA9635,PCA9685alsohasabuilt-inoscillatorforthePWMcontrol.However,thefrequencyusedforPWMcontrolinthePCA9685isadjustablefromabout40Hzto1000Hzascomparedtothetypical97.6kHzfrequencyofthePCA9635.ThisallowstheuseofPCA9685withexternalpowersupplycontrollers.Allbitsaresetatthesamefrequency.•ThePower-OnReset(POR)defaultstateofLEDnoutputpinsisLOWinthecaseofPCA9685.ItisHIGHforPCA9635.TheactiveLOWOutputEnableinputpin(OE)allowsasynchronouscontroloftheLEDoutputsandcanbeusedtosetalltheoutputstoadefinedI2C-busprogrammablelogicstate.TheOEcanalsobeusedtoexternally‘pulsewidthmodulate’theoutputs,whichisusefulwhenmultipledevicesneedtobedimmedorblinkedtogetherusingsoftwarecontrol.SoftwareprogrammableLEDAllCallandthreeSubCallI2C-busaddressesallowallordefinedgroupsofPCA9685devicestorespondtoacommonI2C-busaddress,allowingforexample,allredLEDstobeturnedonoroffatthesametimeormarqueechasingeffect,thusminimizingI2C-buscommands.Sixhardwareaddresspinsallowupto62devicesonthesamebus.TheSoftwareReset(SWRST)GeneralCallallowsthemastertoperformaresetofthePCA9685throughtheI2C-bus,identicaltothePower-OnReset(POR)thatinitializestheregisterstotheirdefaultstatecausingtheoutputstobesetLOW.Thisallowsaneasyandquickwaytoreconfigurealldeviceregisterstothesameconditionviasoftware.PCA9685主要特性和优势:16LEDdrivers.Eachoutputprogrammableat:OffOnProgrammableLEDbrightnessProgrammableLEDturn-ontimetohelpreduceEMI1MHzFast-modePluscompatibleI2C-businterfacewith30mAhighdrivecapabilityonSDAoutputfordrivinghighcapacitivebuses4096-step(12-bit)linearprogrammablebrightnessperLEDoutputvaryingfromfullyoff(default)tomaximumbrightnessLEDoutputfrequency(allLEDs)typicallyvariesfrom40Hzto1000Hz(Defaultof1EhinPRE_SCALEregisterresultsina200Hzrefreshratewithoscillatorclockof25MHz.)Sixteentotempoleoutputs(sink25mAandsource10mAat5V)withsoftwareprogrammableopen-drainLEDoutputsselection(defaultattotempole).Noinputfunction.OutputstatechangeprogrammableontheAcknowledgeortheSTOPCommandtoupdateoutputsbyte-by-byteorallatthesametime(defaultto‘ChangeonSTOP’).ActiveLOWOutputEnable(OE)inputpin.LEDnoutputsprogrammabletologic1,logic0(defaultatpower-up)or‘high-impedance’whenOEisHIGH.6hardwareaddresspinsallow62PCA9685devicestobeconnectedtothesameI2C-busTogglingOEallowsforhardwareLEDblinking4softwareprogrammableI2C-busaddresses(oneLEDAllCalladdressandthreeLEDSubCalladdresses)allowgroupsofdevicestobeaddressedatthesametimeinanycombination(forexample,oneregisterusedfor‘AllCall’sothatallthePCA9685sontheI2C-buscanbeaddressedatthesametimeandthesecondregisterusedforthreedifferentaddressessothat1⁄3ofalldevicesonthebuscanbeaddressedatthesametimeinagroup).SoftwareenableanddisablefortheseI2C-busaddress.SoftwareResetfeature(SWRSTGeneralCall)allowsthedevicetoberesetthroughtheI2C-bus25MHztypicalinternaloscillatorrequiresnoexternalcomponentsExternal50MHz(max.)clockinputInternalpower-onresetNoi