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ApplicationReportSLUA609–September2011SynchronizingThreeorMoreUCC28950Phase-Shifted,Full-BridgeControllersJohnStevens.....................................................................................High-PerformanceIsolatedPowerABSTRACTOneofthekeyfeaturesoftheUCC28950phase-shifted,full-bridgecontrollerisitsabilitytosynchronizeitsmainoscillatortoanexternalclocksource.Inthisway,multiplecontrollerscanbesynchronizedtoimproveperformancecriteriaoftheendpowersupply.ThisapplicationreportexpandsthedetailsofthesynchronizationcapabilityoftheUCC28950,providesexamplesofsimplecircuitsusedtogeneratetheproperclockinputstotheUCC28950,andgivesexamplesoftheinputandoutputsignalingthatcanbeexpectedwiththree-andfour-phaseapplications.Contents1Introduction..................................................................................................................22CharacteristicsoftheSYNCCapabilityintheUCC28950............................................................22.1MinimumSYNC_INFrequency..................................................................................32.2MinimumSYNC_INAmplitude...................................................................................42.3MinimumSYNC_INPulseWidth.................................................................................53ExampleofaFour-PhaseUCC28950PSFB............................................................................54ExampleofaThree-PhaseUCC28950PSFB.........................................................................115Conclusion..................................................................................................................13AppendixAUCC28950ControlCardSchematicandLayout.............................................................15ListofFigures1MinimumSYNCFrequency................................................................................................32MinimumAmplitudetoSYNC(at12Vin,300-nsPW,and200kHz)................................................43MinimumPulseWidthtoSYNC(at12Vin,2.8V,200kHz)..........................................................54OutputSignalsRising-EdgeTimingFlow................................................................................65InputSignalstoSYNCPinsofFour-PhaseUCC28950PSFBConverter(50%D,200kHz)....................76OutputSignalsFromOUTAPinsofEachoftheFourUCC28950Controllers.....................................87InputSignalstoSYNCPinsofFour-PhaseUCC28950PSFBConverter(10%D,200kHz)....................98OutputSignalsFromOUTAPinsofEachoftheFourUCC28950Controllers.....................................99Four-BitShift-RegistertoGenerateFour,Phase-shiftedSYNCSignalsFromaSingleClockSource........1010WaveformsofDual,Four-Bit,Shift-RegisterCircuit..................................................................1111InputSignalstoSYNCPinsofThree-PhaseUCC28950PSFBConverter(50%D,200kHz).................1212OutputSignalsFromOUTAPinsofEachoftheThreeUCC28950Controllers..................................1213UCC28950SmallControlCardSchematic............................................................................1514UCC28950SmallControlCardLayoutandAssembly...............................................................161SLUA609–September2011SynchronizingThreeorMoreUCC28950Phase-Shifted,Full-BridgeControllersSubmitDocumentationFeedbackCopyright©2011,TexasInstrumentsIncorporatedIntroduction(suchasanMSP430).Thisclock,usedwithaserial-in/parallel-outshiftregistersuchasaCD4015,(showninFigure9),canbeusedtogeneratealltheinputSYNCsignalsneeded.Withthismasterclockavailable,thethreeormoreUCC28950controllersareallconfiguredasslaveswithacertainphase-adjustmentamongthemandthen