Features
FullyqualifiedtoClassHorK
-55°Cto+125°Coperation
16to40VDCinput
FullyIsolated
Radhardoptocouplerfeedback
Fixedfrequency,550kHztypical
Topology–SingleEndedForward
Transientprotection50V/120ms
Inhibitfunction
Syncfunction
Indefiniteshortcircuitprotection
Undervoltagelockout
Upto82%efficiency
description
TheSMHFSeriesof28VDC/DCconvertersoffersawide
inputvoltagerangeof16to40voltsandupto15wattsof
outputpower.Theunitsarecapableofwithstandingshortterm
transientsupto50volts.Thepackageisahermeticallysealed,
projection-weldedmetalcase.Flangedandnon-flangedmodels
areavailable.
Screening
SMHFconvertersofferscreeningoptionstoSpacePrototype(O),
ClassH,orClassK.RadiationtoleranttoRadiationHardness
Assurance(RHA)levelsof“-”(O)or“R”,perMIL-PRF-38534.
Interpointmodelnumbersusean“O”intheRHAdesignatorposi-
tiontoindicatethe“-”(dash)RadiationHardnessAssurancelevel
ofMIL-PRF-38534,whichisdefinedas“noRHA”.See“ClassH
andK,MIL-PRF-38534Screening”tablesformoreinformation.
converter DeSign
TheSMHFconvertersareswitchingregulatorsthatuseaquasi-
squarewave,single-endedforwardconverterdesignwitha
constantswitchingfrequencyof550kHz.Isolationbetweeninput
andoutputcircuitsisprovidedwithatransformerintheforward
pathandatemperaturecompensatedopto-couplerinthefeed-
backcontrolloop.Theopto-couplerisradiationhardenedandis
especiallyselectedforspaceapplications.
FortheSMHFdualoutputmodels,crossregulationismaintained
bytightlycoupledoutputmagnetics.Upto70%ofthetotaloutput
powerisavailablefromeitheroutput,providingtheopposite
outputissimultaneouslycarrying30%ofthetotaloutputpower.
Predictablecurrentlimitisaccomplishedbydirectlymonitoring
theoutputloadcurrentandprovidingaconstantcurrentoutput
abovetheoverloadpoint.
HigHer Power DenSity
TheSMHFSeriesoffersanewstandardofperformanceforsmall
sizeandhighpowerdensity.Atjust0.33inchhighandatotal
footprintof1.7in2,thislowprofilepackageoffersatotalpower
densityofupto30wattspercubicinch.
Low noiSe, HigH AuDio rejection
TheSMHFconverter’sfeed-forwardcompensationsystem
providesexcellentdynamicresponseandnoiserejection.Audio
rejectionistypically50dB.Typicaloutputvoltageresponsefor
a50%to100%steploadtransientisaslowas1.3%witha150
Srecoverytime.Inputripplecurrentistypically35mAp-pwith
outputripplevoltagetypically50mVp-p.
inHibit Function
SMHFconvertersprovideaninhibitterminalthatcanbeused
todisableinternalswitching,resultinginnooutputandverylow
quiescentinputcurrent.Theconverterisinhibitedwhenalogic
low(≤0.8–outputdisabled)isappliedtotheinhibitpin.The
unitisenabledwhenthepin,whichisinternallyconnectedtoa
pull-upresistor,isleftunconnectedorisconnectedtoanopen-
collectorgate.Theopencircuitoutputvoltageassociatedwiththe
inhibitpinis8.5to12VDC.Intheinhibitmode,amaximumof
4mAmustbesunkfromtheinhibitpinat28VDCinput.
models
vDc
SIngLE
2.5
3.3
5
12
15
DUAL
±5
±12
±15
ClearedbyU.S.DoDOSRforPublicRelease
OSRcasenumber09S-0995,datedMarch13,2009.
Crane Aerospace & Electronics Power Solutions
smHF single and dual dc/dc converters
CraneAerospace&Electronics
Electronicsgroup(InterpointBrand)
POBox97005RedmondWA98073-9705
425.882.3100electronics@craneae.com
www.craneae.com
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RevD-20070404
28 Volt input – 15 Watt