UCx84x Current-Mode PWM Controllers - TI.com

1 VINUC2843 VCCVREFRT/CTGROUNDCOMPVFBISENSEOUTPUTC opyright 2016, Texas Instruments IncorporatedProductFolderOrderNowTechnic alDocumentsTools &SoftwareSupport &CommunityAn IMPORTANTNOTICEat the end of this datasheetaddressesavailability,warranty, changes,use in safety-criticalapplications,intellectual propertymattersand ,UC2842,UC3842,UC1843,UC2843,UC3843UC184 4,UC2844,UC3844,UC1845,UC2845,UC3845 SLUS223F APRIL1997 REVISEDAPRIL2020 UCx84xCurrent-ModePWM Controllers1 Features11 Optimizedfor off-lineand DC-to-DCconverters Low start-upcurrent(< 1 mA)

2 Automaticfeedforwardcompensation Pulse-by-pulsecurrentlimiting Enhancedload-responsecharacteristics Undervoltagelockoutwith hysteresis Double-pulsesuppression High-currenttotem-poleoutput Internallytrimmedbandgapreference Up to 500-kHzoperation Erroramplifierwith low outputresistance2 Applications Switchingregulatorsof any polarity Transformer-coupledDC-DCconverters3 DescriptionTheUCx84xseriesof controlintegratedcircuitsprovidethe featuresthat are necessaryto implementoff-lineor DC-to-DCfixed-frequencycurrent-modecontr olschemes,with a minimumnumberof undervoltagelockout(UVLO),featuringastar t-upcurrentof lessthan1 mA,and a precisionreferencetrimmedfor accuracyat the ensurelatchedoperation,a pulse-widthmodulation(PWM)

3 Comparatorthatalsoprovidescurrent-limitc ontrol,anda totem-poleoutputstagethatis designedtosourceor outputstage,suitablefor drivingN-channelMOSFETs,is low whenit is in the off varietyof packageoptions,temperaturerangeoptions,c hoiceofmaximumduty cycle,and choiceof turnonand turnoffhysteresisare idealchoicesfor off-linepowersupplies,whilethe deviceswithanarrowerhysteresisrangeare suitedfor specifiedforoperationfrom 55 C to 125 C, the UC284xseriesisspecifiedfor operationfrom 40 C to 85 C, and theUC384xseriesis specifiedfor operationfrom0 C to70 (1)PARTNUMBERPACKAGE(PIN)BODYSIZE(NOM)UC 184xCDIP(8) (20) (8) (8) (14) (8) (8) (14) (8) (8) (1) For all availablepackages,see the orderableaddendumatthe end of the ,UC2842,UC3842,UC1843,UC2843,UC3843UC184 4,UC2844,UC3844,UC1845,UC2845,UC3845 SLUS223F APRIL1997.

4 UC1842UC2842UC3842UC1843UC2843UC3843UC18 44UC2844UC3844UC1845UC2845UC3845 SubmitDocumentationFeedbackCopyright 1997 2020,TexasInstrumentsIncorporatedTableof Contents1 Pin Configurationand Applicationand Deviceand Mechanical,Packaging,and RevisionHistoryNOTE:Pagenumbersfor previousrevisionsmay differfrompagenumbersin the (January2017)to RevisionFPage (August2016)to RevisionEPage (June2007)to RevisionDPage AddedESDR atingstable,FeatureDescriptionsection,De viceFunctionalModes,Applicationand Implementationsection,PowerSupplyRecomme ndationssection,Layoutsection,Deviceand DocumentationSupportsection,andMechanica l,Packaging,and Changedvaluesin 10 11 12 133 2 1 20 19181716151445678 VCCVCNCOUTPUTNCNCVFBNCISENSENCNCRT/CTNCP WRGNDGROUNDNCCOMPNCVREFNC123456714131211 1098 VCCVCPWRGNDCOMPNCVFBNCISENSENCRT/CTGROUN DOUTPUTVREFNCOUTPUTVCCVREFGROUNDVFBCOMPI SENSERT/CT123487653UC1842,UC2842,UC3842, UC1843.

5 UC2843,UC3843UC1844,UC2844,UC3844,UC1845 ,UC2845, APRIL1997 REVISEDAPRIL2020 ProductFolderLinks:UC1842UC2842UC3842UC1 843UC2843UC3843UC1844UC2844UC3844UC1845U C2845UC3845 SubmitDocumentationFeedbackCopyright 1997 2020,TexasInstrumentsIncorporated5 DeviceComparisonTableUVLOTEMPERATURERANG EMAXDUTYCYCLETURNONAT 16 VTURNOFFAT 10 VSUITABLEFOROFF-LINEAPPLICATIONSTURNONAT VTURNOFFAT VSUITABLEFORDC-DCAPPLICATIONSUC1842UC184 3 55 C to 125 CUp to 100%UC2842UC2843 40 C to 85 CUC3842UC38430 C to 70 CUC1844UC1845 55 C to 125 CUp to 50%UC2844UC2845 40 C to 85 CUC3844UC38450 C to 70 C6 Pin Configurationand FunctionsD.

6 JG, and P Packages8-PinSOIC,CDIP,and PDIPTop ViewD and W Packages14-PinSOICand CFPTop ViewFK Package20-PinLCCCTop ViewIOUTPUT= Qg fSWfOSC= CCT4UC1842,UC2842,UC3842,UC1843,UC2843,U C3843UC1844,UC2844,UC3844,UC1845,UC2845, UC3845 SLUS223F APRIL1997 :UC1842UC2842UC3842UC1843UC2843UC3843UC1 844UC2844UC3844UC1845UC2845UC3845 SubmitDocumentationFeedbackCopyright 1997 2020,TexasInstrumentsIncorporatedPin FunctionsPINTYPEDESCRIPTIONNAMESOIC,CDIP ,PDIP(8)SOIC,CFP(14)LCCC(20)COMP112 OErroramplifiercompensationpin. Connectexternalcompensationcomponentsto this pin to modifythe erroramplifieris internallycurrent-limitedso the usercan commandzeroduty cycleby externallyforcingCOMPto devicepackageswithoutPWRGND,GROUND functionsas bothpowergroundand devicepackageswithoutPWRGND,GROUND functionsas bothpowergroundand analoggroundISENSE357 IPrimary-sidecurrentsensepin.

7 Connectto PWMusesthis signalto terminatethe voltagerampcan be appliedto this pin to run thedevicewith a 2, 4, 6, 131, 3, 4, 6,8, 9, 11,14, 16, 19 Do not connectOUTPUT61015 OOUTPUTis the gatedrivefor the theoutputof the on-chipdriverstageintendedto up to 1 A are sourcedand sunkby thispin. OUTPUTis activelyheld low whenVCCis belowthe ,RRT, toVREFand timingcapacitor,CCT, to GROUND fromthis pin to set best performance,keepthe timingcapacitorlead to the deviceGROUNDas shortand directas ,use separategroundtracesfor the timingcapacitorand frequencyof the oscillatorcan be estimatedwith the followingequations:(1)wherefOSCis in Hertz,RRTis in Ohmsand CCTis in a timingresistorless than5 k.

8 The frequencyof the OUTPUT gatedriveof the UCx842and UCx843,fSW, is equalto fOSCat up to100%duty cycle;the frequencyof the UCx844and UCx845is equalto half of the fOSCfrequencyat up to 50%duty 1117 IBiassupplyinputfor the PWMcontrollersthatdo not havethis pin, the gatedriveris biasedfromthe VCCpin. VCmusthavea bypasscapacitorat least10 timesgreaterthanthe gatecapacitanceof the mainswitchingFET usedin the inputthat providespowerto the the sum of the quiescentVCCcurrentand switchingfrequencyand theMOSFET gatecharge,Qg, the averageOUTPUT currentcan becalculatedfrom:(2)A bypasscapacitor, F, connecteddirectlyto GROUND withminimaltracelength,is requiredon this pin.

9 An additionalbypasscapacitorat least10 timesgreaterthanthe gatecapacitanceof the mainswitchingFETusedin the designis the usedto controlthe powerconvertervoltage-feedbackloop for ,UC2842,UC3842,UC1843,UC2843,UC3843UC184 4,UC2844,UC3844,UC1845,UC2845, APRIL1997 REVISEDAPRIL2020 ProductFolderLinks:UC1842UC2842UC3842UC1 843UC2843UC3843UC1844UC2844UC3844UC1845U C2845UC3845 SubmitDocumentationFeedbackCopyright 1997 2020,TexasInstrumentsIncorporatedPin Functions(continued)PINTYPEDESCRIPTIONNA MESOIC,CDIP,PDIP(8)SOIC,CFP(14)LCCC(20)

10 VREF81420O5-V usedto providechargingcurrenttothe oscillatortimingcapacitorthroughthe isimportantfor referencestabilitythat VREFis bypassedto GROUND with a ceramiccapacitorconnectedas closeto the pin as F ceramicis requiredfor externalloadson ,UC2842,UC3842,UC1843,UC2843,UC3843UC184 4,UC2844,UC3844,UC1845,UC2845,UC3845 SLUS223F APRIL1997 :UC1842UC2842UC3842UC1843UC2843UC3843UC1 844UC2844UC3844UC1845UC2845UC3845 SubmitDocumentationFeedbackCopyright 1997 2020,TexasInstrumentsIncorporated(1)Stre ssesbeyondthoselistedunderAbsoluteMaximu mRatingsmay causepermanentdamageto the stressratingsonly,whichdo not implyfunctionaloperationof the deviceat theseor any otherconditionsbeyondthoseindicatedunder RecommendedOperatingConditions.