ZXCT1010-电流监控芯片

1ISSUE10-JULY2007SEMICONDUCTORSZXCT1010DESCRIPTIONTheZXCT1010isahighsidecurrentsensemonitor.Usingthisdeviceeliminatestheneedtodisruptthegroundplanewhensensingaloadcurrent.ItisanenhancedversionoftheZXCT1009offeringreducedtypicaloutputoffsetandimprovedaccuracyatlowsensevoltage.Thewideinputvoltagerangeof20Vdowntoaslowas2.5Vmakeitsuitableforarangeofapplications.Aminimumoperatingcurrentofjust4µA,combinedwithitsSOT23-5packagemakesuitableforportablebatteryequipment.FEATURES•Lowcost,accuratehigh-sidecurrentsensing•Outputvoltagescaling•Upto2.5Vsensevoltage•2.5V–20Vsupplyrange•300nAtypicaloffsetcurrent•3.5µAquiescentcurrent•1%typicalaccuracy•SOT23-5packageAPPLICATIONS•Batterychargers•Smartbatterypacks•DCmotorcontrol•Overcurrentmonitor•Powermanagement•ProgrammablecurrentsourceENHANCEDHIGH-SIDECURRENTMONITORAPPLICATIONCIRCUITDEVICEREELSIZETAPEWIDTHQUANTITYPERREELZXCT1010E5TA7”8mm3,000unitsPARTMARK101PACKAGESOT23-5ORDERINGINFORMATIONSEMICONDUCTORSZXCT1010ABSOLUTEMAXIMUMRATINGSVoltageonanypin-0.6Vto20V(relativetoGND)Continuousoutputcurrent,IOUT,25mAContinuoussensevoltage,VSENSE2,-0.5Vto+5VOperatingtemperature,TA,-40to85°CStoragetemperature-55to150°CPackagepowerdissipation(TA=25°C)SOT23-5300mWOperationabovetheabsolutemaximumratingmaycausedevicefailure.Operationattheabsolutemaximumratings,forextendedperiods,mayreducedevicereliability.ELECTRICALCHARACTERISTICSTestConditionsTA=25°C,Vin=5V,Rout=100Ω.SYMBOLPARAMETERCONDITIONSLIMITSUNITMinTypMaxVinVCCRange2.520VIout1OutputcurrentVsense=0VVsense=10mVVsense=100mVVsense=200mVVsense=1V0850.9751.959.70.31001.002.0010.0101151.0252.0510.3µAµAmAmAmAIqGroundpincurrentVsense=0V3.58µAVsense2SenseVoltage02500mVIsense-Vsense-inputcurrent100nAAccAccuracyRsense=0.1ΩVsense=200mV-2.52.5%GmTransconductance,Iout/Vsense10000µA/VBWBandwidthVSENSE(DC)=10mV,Pin=-40dBm‡VSENSE(DC)=100mV,Pin=-20dBm‡3002kHzMHz1Includesinputoffsetvoltagecontribution2VSENSEisdefinedasthedifferentialvoltagebetweenVSENSE+andVSENSE-.VSENSE=VSENSE+-VSENSE-=VIN-VLOAD=ILOADxRSENSE3-20dBm=63mVp-pinto50ΩISSUE10-JULY2007ISSUE10-JULY2007SEMICONDUCTORSZXCT10103TYPICALCHARACTERISTICS4ISSUE10-JULY2007SEMICONDUCTORSZXCT1010PINDESCRIPTIONPinNamePinFunctionVsense+SupplyvoltageVsense-Connectiontoload/batteryIoutOutputcurrent,proportionaltoVin-VloadGNDGroundSOT23-5PackageSuffix–E5TopViewCONNECTIONDIAGRAMSCHEMATICDIAGRAMISSUE10-JULY2007SEMICONDUCTORSZXCT10105Thefollowinglinesdescribehowtoscalealoadcurrenttoanoutputvoltage.Vsense=Vin-VloadVout=0.01xVsensexRout1E.g.A1Acurrentistoberepresentedbya100mVoutputvoltage:1)ChoosethevalueofRsensetogive50mVVsense500mVatfullload.ForexampleVsense=100mVat1.0A.Rsense=0.1/1.0=0.1ohms.2)ChooseRouttogiveVout=100mV,whenVsense=100mV.Rearranging1forRoutgives:Rout=Vout/(Vsensex0.01)Rout=0.1/(0.1x0.01)=100ΩTYPICALCIRCUITAPPLICATIONPOWERDISSIPATIONThemaximumallowablepowerdissipationofthedevicefornormaloperation(Pmax),isafunctionofthepackagejunctiontoambientthermalresistance(θja),maximumjunctiontemperature(Tjmax),andambienttemperature(Tamb),accordingtotheexpression:Pmax=(Tjmax–Tamb)/θjaThedevicepowerdissipation,PDisgivenbytheexpression:PD=Iout.(Vin-Vout)WattsWhereRloadrepresentsanyloadincludingDCmotors,achargingbatteryorfurthercircuitrythatrequiresmonitoring,Rsensecanbeselectedonspecificrequirementsofaccuracy,sizeandpowerrating.APPLICATIONSINFORMATIONISSUE10-JULY2007SEMICONDUCTORSZXCT10106Li-IonChargerCircuitTheabovefigureshowstheZXCT1010supportingtheBenchmarqbq2954ChargeManagementIC.Mostofthesupportcomponentsforthebq2954areomittedforclarity.ThisdesignalsousestheZetexFZT789AhighcurrentSuper-PNPastheswitchingtransistorintheDC-DCstepdownconverterandtheFMMT451asthedriveNPNfortheFZT789A.ThecircuitcanbeconfiguredtochargeuptofourLi-Ioncellsatachargecurrentof1.25A.Chargecanbeterminatedonmaximumvoltage,selectableminimumcurrent,ormaximumtimeout.SwitchingfrequencyofthePWMloopisapproximately120kHz.100Ω0.2Ω100ΩFZT789ABC817251kΩBAS1610µHFMMT451140µHZHCS1000220ΩSNSpinMODpinChargerInputToBattery+bq29545VZXCT1010supportcomponentsomittedforclarity+-VinLoadIoutAPPLICATIONSINFORMATION(Continued)Bi-DirectionalCurrentSensingTheZXCT1010canbeusedtomeasurecurrentbi-directionally,iftwodevicesareconnectedasshownbelow.IfthevoltageV1ispositivewithrespecttothevoltageV2thelowerdevicewillbeactive,deliveringaproportionaloutputcurrenttoRout.DuetothepolarityofthevoltageacrossRsense,theupperdevicewillbeinactiveandwillnotcontributetothecurrentdeliveredtoRout.WhenV2ismorepositivethanV1,currentwillbeflowingintheoppositedirection,causingtheupperdevicetobeactiveinstead.Non-linearitywillbeapparentatsmallvaluesofVsenseduetooffsetcurrentcontribution.Devicescanuseseparateoutputresistorsifthecurrentdirectionistobemonitoredindependently.Bi-directionalTransferFunction-400-2000200400012345OutputCurrent(mA)SenseVoltage(mV)OutputCurrentvSenseVoltageISSUE10-JULY2007SEMICONDUCTORSZXCT10107PCBtraceshuntresistorforlowcostsolutionThefigurebelowshowsoutputcharacteristicsofthedevicewhenusingaPCBresistivetraceforalowcostsolutioninreplacementforaconventionalshuntresistor