LM5118

LM5118/LM5118QMarch8,2010WideVoltageRangeBuck-BoostControllerGeneralDescriptionTheLM5118widevoltagerangeBuck-Boostswitchingregu-latorcontrollerfeaturesallofthefunctionsnecessarytoim-plementahighperformance,costefficientBuck-Boostregulatorusingaminimumofexternalcomponents.TheBuck-Boosttopologymaintainsoutputvoltageregulationwhentheinputvoltageiseitherlessthanorgreaterthantheoutputvoltagemakingitespeciallysuitableforautomotiveapplications.TheLM5118operatesasabuckregulatorwhiletheinputvoltageissufficientlygreaterthantheregulatedout-putvoltageandgraduallytransitionstothebuck-boostmodeastheinputvoltageapproachestheoutput.Thisdualmodeapproachmaintainsregulationoverawiderangeofinputvoltageswithoptimalconversionefficiencyinthebuckmodeandaglitch-freeoutputduringmodetransitions.ThiseasytousecontrollerincludesdriversforthehighsidebuckMOSFETandthelowsideboostMOSFET.Theregulator’scontrolmethodisbaseduponcurrentmodecontrolutilizinganem-ulatedcurrentramp.Emulatedcurrentmodecontrolreducesnoisesensitivityofthepulse-widthmodulationcircuit,allow-ingreliablecontroloftheverysmalldutycyclesnecessaryinhighinputvoltageapplications.Additionalprotectionfeaturesincludecurrentlimit,thermalshutdownandanenableinput.ThedeviceisavailableinapowerenhancedTSSOP-20packagefeaturinganexposeddieattachpadtoaidthermaldissipation.Features■LM5118QisanAutomotiveGradeproductthatisAEC-Q100grade1qualified(-40°Cto125°Coperatingjunctiontemperature)■Ultra-wideinputvoltagerangefrom3Vto75V■Emulatedpeakcurrentmodecontrol■Smoothtransitionbetweenstep-downandstep-upmodes■Switchingfrequencyprogrammableto500KHz■Oscillatorsynchronizationcapability■Internalhighvoltagebiasregulator■Integratedhighandlow-sidegatedrivers■Programmablesoft-starttime■Ultralowshutdowncurrent■Enableinputwidebandwidtherroramplifier■1.5%feedbackreferenceaccuracy■ThermalshutdownPackageTSSOP-20EP(Exposedpad)TypicalApplicationCircuit30058501©2010NationalSemiconductorCorporation300585*LM5118Q1MHXTSSOP-20EPMXA20A2500unitsshippedasTape&Reel*AutomotiveGrade(Q)productincorporatesenhancedmanufacturingandsupportprocessesfortheautomotivemarket,includingdefectdetectionmethodologies.ReliabilityqualificationiscompliantwiththerequirementsandtemperaturegradesdefinedintheAEC-Q100standard.AutomotivegradeproductsareidentifiedwiththeletterQ.Formoreinformationgoto(VCCregulatorrunning,switchingregulatordisabled).WhentheUVLOpinexceeds1.23V,theregulatorentersthenormaloperatingmode.Anexternalvoltagedividercanbeusedtosetanunder-voltageshutdownthreshold.Afixed5µAcurrentissourcedoutoftheUVLOpin.Ifacurrentlimitconditionexistsfor256consecutiveswitchingcycles,aninternalswitchpullstheUVLOpintogroundandthenreleases.3RTTheinternaloscillatorfrequencyissetwithasingleresistorbetweenthispinandtheAGNDpin.Therecommendedfrequencyrangeis50kHzto500kHz.4ENIftheENpinisbelow0.5V,theregulatorwillbeinalowpowerstatedrawinglessthan10µAfromVIN.ENmustberaisedabove3Vfornormaloperation.5RAMPRampcontrolsignal.AnexternalcapacitorconnectedbetweenthispinandtheAGNDpinsetstherampslopeusedforemulatedcurrentmodecontrol.6AGNDAnalogground.7SSSoft-Start.Anexternalcapacitorandaninternal10µAcurrentsourcesettherisetimeoftheerrorampreference.TheSSpinisheldlowwhenVCCislessthantheVCCunder-voltagethreshold(3.7V),whentheUVLOpinislow(1.23V),whenENislow(0.5V)orwhenthermalshutdownisactive.8FBFeedbacksignalfromtheregulatedoutput.Connecttotheinvertinginputoftheinternalerroramplifier.9COMPOutputoftheinternalerroramplifier.TheloopcompensationnetworkshouldbeconnectedbetweenCOMPandtheFBpin.10VOUTOutputvoltagemonitorforemulatedcurrentmodecontrol.Connectthispindirectlytotheregulatedoutput.