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PKJ4000EPIEN/LZT146025R8AEricssonPowerModules,June2007
Operating Information
Over Temperature Protection (OTP)
ThePKJ4000ESeriesDC/DCconvertersareprotectedfrom
thermaloverloadbyaninternalovertemperatureshutdown
circuit.WhenthePCBtemperature(centreofPCB)exceeds
135°Ctheconverterwillshutdownimmediately(latching).
Theconvertercanberestartedbycyclingtheinputvoltage
orusingtheremotecontrolfunction.
Input And Output Impedance
Theimpedanceofboththepowersourceandtheloadwill
interactwiththeimpedanceoftheDC/DCconverter.Itis
mostimportanttohavearatiobetweenLandCaslow
aspossible,i.e.alowcharacteristicimpedance,bothat
theinputandoutput,astheconvertershavealowenergy
storagecapability.ThePKJ4000ESeriesDC/DCconverters
havebeendesignedtobecompletelystablewithoutthe
needforexternalcapacitorsontheinputortheoutput
circuits.Theperformanceinsomeapplicationscanbe
enhancedbyadditionofexternalcapacitanceasdescribed
undermaximumcapacitiveload.Ifthedistributionofthe
inputvoltagesourcetotheconvertercontainssignificant
inductance,theadditionofa100Fcapacitoracrossthe
inputoftheconverterwillhelpinsurestability.Thiscapacitor
isnotrequiredwhenpoweringtheDC/DCconverterfrom
alowimpedancesourcewithshort,lowinductance,input
powerleads.
Parallel Operation
ThePKJ4000ESeriesDC/DCconverterscanbeparalleled
forredundancyifexternal"O"-ringdiodesareusedinseries
withtheoutputs.ItisnotrecommendedtoparallelthePKJ
4000ESeriesDC/DCconvertersforincreasedpowerwithout
usingexternalcurrentsharingcircuits.
Maximum Capacitive Load
Whenpoweringloadswithsignificantdynamiccurrent
requirements,thevoltageregulationattheloadcanbe
improvedbyadditionofdecouplingcapacitanceatthe
load.ThemostaffectivetechniqueistolocatelowESR
ceramiccapacitorsasclosetotheloadaspossible,using
severalcapacitorstolowertheeffectiveESR.These
ceramiccapacitorswillhandleshortdurationhigh-frequency
componentsofdynamicloadchanges.Inaddition,higher
valuesofelectrolyticcapacitorsshouldbeusedtohandle
themid-frequencycomponents.Itisequallyimportant
tousegooddesignpractisewhenconfiguringtheDC
distributionsystem.
LowresistanceandlowinductancePCB(printedcircuit
board)layoutsandcablingshouldbeused.Rememberthat
whenusingremotesensing,allresistance,inductanceand
capacitanceofthedistributionsystemiswithinthefeedback
loopoftheconverter.Thiscanaffectontheconverters
compensationandtheresultingstabilityanddynamic
responseperformance.Asa“ruleofthumb”,100F/Aof
outputcurrentcanbeusedwithoutanyadditionalanalysis.
Forexamplewitha25Aconverter,valuesofdecoupling
capacitanceupto2500Fcanbeusedwithoutregardto
stability.Withlargervaluesofcapacitance,theloadtransient
recoverytimecanexceedthespecifiedvalue.Asmuchof
thecapacitanceaspossibleshouldbeoutsidetheremote
sensingloopandclosetotheload.Theabsolutemaximum
valueofoutputcapacitanceis10000F.Forvalueslarger
thanthis,pleasecontactyourlocalEricssonPowerModules
representative.
Current Limit Protection
ThePKJ4000ESeriesDC/DCconvertersincludecurrent
limitingcircuitrythatallowsthemtowithstandcontinuous
overloadsorshortcircuitconditionsontheoutput.Theout-
putvoltagewilldecreasetowardszeroforoutputcurrentsin
excessofmaxoutputcurrent(Iomax).
Theconverterwillresumenormaloperationafterremoval
oftheoverload.Theloaddistributionsystemshouldbe
designedtocarrythemaximumoutputshortcircuitcurrent
specified.
Over Voltage Protection (OVP)
ThePKJ4000ESeriesDC/DCconvertershavelatching
outputovervoltageprotection.Intheeventofanovervolt-
agecondition,theconverterwillshutdownimmediately.The
convertercanberestartedbycyclingtheinputvoltageor
usingtheremotecontrolfunction.