矽力杰 Silergy SY52251 次级同步整流转换器 规格书 Datasheet 佰祥电子

SY52251

SecondarySideSynchronousRectificationConverter

GeneralDescriptionFeatures

SmartTurnoffTechnology

SY52251isahigh-performancesynchronousrectifier

Secondary-sideSynchronousRectifierfor

whichcontainscontrollerandMOSFETdevices.This

5V~12VSystems

solutionnotonlydirectlyreducespowerdissipationof

therectifierbutalsoindirectlyreducesprimary-sideSuitableforDiscontinuousMode(DCM),Critical

losses,duetocompoundingofefficiencygains.TheConductionMode(CRM)

DRAINpinofSY52251cansupport60VvoltageSuitableforPrimarySideRegulation(PSR),

stress.SecondarySideRegulation(SSR)

RoHSCompliantandHalogenFree

SY52251willachieveultra-lowpowerconsumptionCompactPackage:SO8

whenthecircuitoperatesinnoload.

TheSY52251isavailableinacompactSO8package.Applications

AC/DCAdapters

BatteryChargers

ConsumerElectronics

AuxiliaryPowerSupplies

Recommendedoperatingoutputpower

ProductsVOUT=5VVOUT=12V

SY522513.4A3A

TypicalApplication

RS1CS1

DB1VOUT+

SOURCEDRAIN

L

R5C3SOURCEDRAIN

C1C2

R6SOURCEDRAIN

CS3RS2

ND1

VCCDRAINCS2

R7

SY52251

R1

D2PrimarySideSwitcherVOUT-

R3

VINDRAIN

C4

GNDDRAIN

VSEN

R4DRAIN

ISENDRAIN

R2

Fig.1TypicalApplicationCircuitinHighSide

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SY52251

DB1VOUT+

L

R5C3

C1C2SY52251

R6DRAINVCC

RS2

ND1CS3

DRAINCS2

R7SOURCE

DRAINSOURCE

R1DRAINSOURCE

D2PrimarySideSwitcherVOUT-

R3

VINDRAIN

C4

GNDDRAINCS1RS1

VSEN

R4DRAIN

ISENDRAIN

R2

Fig.2TypicalApplicationCircuitinLowSide

OrderingInformation

SOURCE18DRAIN

SY52251□(□□)□

TemperatureCodeSOURCE27DRAIN

PackageCode

SOURCE36DRAIN

OptionalSpecCode

VCC45DRAIN

Pinout(topview)

OrderingNumberPackageTopMark

SY52251FACSO8CEYxyz

x=yearcode,y=weekcode,z=lotnumbercode

Pinout(topview)

PinnumberPinNamePinDescription

1,2,3SOURCESOURCEoftheinternalpowerMOSFET.

Powersupplypin.Thispinconnectsa0.1μForlargerceramic

4VCC

bypasscapacitor.

5,6,7,8DRAINDRAINoftheinternalpowerMOSFET.

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SY52251

BlockDiagram

VCC

DrainVOLTAGE

LDOCircuitREGULATOR

&UVLO

SR_ON

SR_ON

ON_ThresholdMin_ton/Min_toff&

DrainSR_OFFPWM

PWM

DrainGeneratorDRAIN

SOURCEOFF_ThresholdDRAIN

SR_OFF

SOURCEDRAIN

SOURCEDRAIN

PWMGATE

DRIVER

Mosfet

Fig.3Blockdiagram

AbsoluteMaximumRatings(Note1)

VCC---------------------------------------------------------------------------------------------------------------------------0.3V~16V

DRAIN------------------------------------------------------------------------------------------------------------------------1.5V~60V

IVCC---------------------------------------------------------------------------------------------------------------------------------20mA

PowerDissipation,@TA=25°CSO8-----------------------------------------------------------------------------------------1.1W

PackageThermalResistance(Note2)

SO8,θJA----------------------------------------------------------------------------------------------------------------137°C/W

SO8,θJC------------------------------------------------------------------------------------------------------------------35°C/W

JunctionTemperatureRange------------------------------------------------------------------------------------------45°Cto150°C

LeadTemperature(Soldering,10sec.)----------------------------------------------------------------------------------------260°C

StorageTemperatureRange-------------------------------------------------------------------------------------------65°Cto150°C

RecommendedOperatingConditions

VCC------------------------------------------------------------------------------------------------------------------------------4V~12V

JunctionTemperatureRange------------------------------------------------------------------------------------------40°Cto125°C

AmbientTemperatureRange------------------------------------------------------------------------------------------40°Cto105°C

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SY52251

ElectricalCharacteristics

(VVCC=10V,TA=25°Cunlessotherwisespecified)

ParameterSymbolTestConditionsMinTypMaxUnit

PowerSupplySection

VCCTurn-onThresholdVVCC_ON3.63.753.9V

HysteresisVoltageVHYSTERESIS75115155mV

QuiescentCurrent160200µA

ThresholdSection

On_threshold-240-190-140mV

BlankingTimeSection

MinTonTON_BLANK80012001600ns

MinToffTOFF_BLANK180022002600ns

MOSFETSection

MosfetBreakDownVoltageVDSS(BR)VGS=0V,ID=0.25mA60V

MosfetOn-stateResistorRDS(ON)VGS=10V,ID=5A9mΩ

ContinuousDrainCurrent(Note3)IDTC=25℃10A

PulsedDrainCurrent(Note4)IDM40A

ThermalSection

ThermalShutdownTemperatureTSD150°C

HysteresistoResumeOperatingTOTP_HYS20°C

Note1:Stressesbeyondthe“AbsoluteMaximumRatings”maycausepermanentdamagetothedevice.Thesearefor

stressratingsonly.Functionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedinthe

operationalsectionsofthespecificationisnotimplied.Exposuretoabsolutemaximumratingconditionsforextended

periodsmayaffectdevicereliability.

Note2:θJAismeasuredinthenaturalconvectionatTA=25°Conaloweffectivesinglelayerthermalconductivitytest

boardofJEDEC51-3thermalmeasurementstandard.Testcondition:Devicemountedon2”x2”FR-4substratePCB,

2ozcopper,withminimumrecommendedpadontoplayerandthermalviastobottomlayergroundplan.

Note3:Guaranteebydesign.

Note4:RepetitiveRating:Pulsewidthlimitedbymaximumjunctiontemperature;Guaranteebydesign.

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SY52251

TypicalPerformanceCharacteristics

(Testcondition:inputvoltage:90Vac;outputspec:5Vdc_3.4A;Cable:22#1.2m.Ambienttemperature:25±5℃;

Ambienthumidity:65±25%.)

SteadyStatesSteadyStates

(VIN=115V(AC),fullload)(VIN=230V(AC),fullload)

VDrain5V/div

VDrain5V/div

Time(10µs/div)Time(10µs/div)

SteadyStatesSteadyStates

(VIN=115V(AC),noload)(VIN=230V(AC),noload)

VDrain5V/divVDrain5V/div

Time(10µs/div)Time(10µs/div)

AverageEfficiencyvs.InputVoltage

84

83

82

81

80

79

SY52251

78Level5

Level6

AverageEfficiency(%)EfficiencyAverage77

76

90115230264

InputVoltage(V)

Fig.4AverageEfficiencyCurve

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SY52251

Self-PowerSupply

DescriptionWhenSRturnsoff,thevoltageofDSENwillbepulled

up.IfthevoltageofDSENishigherthanvoltageofVCC,

SRTurnOnthechargingcurrentwillflowtoVCCfromDSEN.As

WhenanegativevoltagelowerthanonthresholdtheDSENexceedtheZenerdiodeD2breakdown

VON_THRissensedontheDSENpin,thedriverlogicvoltage,theVCCwillbeclampedtothevoltage.The

turnsup,thenafteradelaytime,theGATEispulledhigh.chargingcurrentislimitedto30mA(typicalvalue).If

thevoltageofDSENislowerthanvoltageofVCC,the

chargingfunctionisshutdown.AsinFig.6.

AccuracyZeroCurrentTurnoffStrategy

TheinitialturnoffthresholdVOFF_INITIALofSRswitcher

is-30mV(typicalvalue).WhentheDrainvoltageontheV1T1VCC

SRishigherthantheturnoffthreshold,theSRwouldDSEN

turnoffafteradelaytime.D1

V2

SY52251adoptsasmartcontrolstrategytoachieveSRR1

accuracyzerocurrentturnoffbycompensatingtheoffD2C1

thresholdeachswitchingperiod,whichalsomakeSRGND

operatinginhighefficiencyandreliability.

MinTon&MinToffICinternalcircuit

Afterswitch-onoftheSY52251,theinputsignalontheFig.6circuitdiagramofself-powersupply

DRAINpinisblankedduringtheonblankingtime

TON_BLANK.Thisactioneliminatesfalseswitch-offduetoUVLO

highfrequencyringingatthestartofthesecondaryTheICleavestheunder-voltagelockoutstateand

stroke.(SeeON_BLANKinFig.5).activatesthesynchronousrectifiercircuitwhenthe

Afterswitch-offoftheSY52251,theinputsignalonthevoltageontheVCCpinisaboveVVCC_ON.Whenthe

DRAINpinisblankedduringtheoffblankingtime.ThisvoltagedropsbelowVVCC_OFF,theunder-voltagelockout

actioneliminatesfalseswitch-onduetohighfrequencystateisenteredandtheSRdriveroutputisactivelykept

ringingatthestartofthesecondarystroke.(Seelow.AsinFig.7.

OFF_BLANKinFig.5)

VVcc_OFF

RQVcc_up

VCC

VDS

2VSQ

VVcc_ON

Off_threshold

On_threshold

Mistaketurnon

atfirstresonantbottom

Fig.7circuitdiagramofUVLO

VGS

Powerdesign

ON_BLANKAfewapplicationsareshownasbelow.

OFF_BLANKTypicalapplicationspecification

POSITION_BLANKProductsInputrangeOutputTemperaturerise

90Vac~264Vac12V/3A55℃

Fig.5timingdiagramofMin_ton&Min_toffSY52251

90Vac~264Vac5V/3.4A49℃

TopreventSRfalseturnonafterresonantperiodwhichThetestisoperatedinnaturalcoolingconditionat

causedbyprimarymagneticinductorandprimary25℃ambienttemperature.

equivalentcap,theoffblankingtimeisnotenoughto

accomplish.ThepositionblankingtimeTPOSITION_BLANK

canworkout.(SeePOSITION_BLANKinFig.5)

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SY52251

Layout

S-

(a)ToachievebetterEMIandEfficiencyperformance,

1

theoutputconnectorshouldbeconnectedtotheoutputS

capfirst,thentotheSRPowerpin.U1R

2

S

C

(b)Thecircuitloopofallswitchingcircuitshouldbe

CS1

keptsmall:secondarypowerloop,secondaryRC

CS3

snubbercircuitloopandICpowersupplyloop.S+

V-

V+

CS4

Fig.8layoutexample

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SY52251

DesignNotice

1.Atnoload,secondarysidediodefreewheelingtimeshouldbelongerthan1.6usatnoload.

2.ToconsiderthereliabilityofSRswitcherandthestartupperformanceinalltemperaturerange,therecommended

valueofVCCcapacitanceis0.47uF.

3.ToachievebettersystemESDperformance,theVCCcapshouldbeclosetoSRswitcherassoonaspossible.

4.ToachievebetterEMIperformanceandimprovetheefficiency,theloopofsecondaryswitchingcircuitshouldbe

keptassmallaspossible.

5.TopreventSRfalseturnonduringSRoff_thresholdadjustmentstage,theprimaryswitchshouldbeturnedon

beforesecondDCMresonantbottom.

6.TopreventprimaryandsecondaryswitchconductatthesametimewhencircuitoperatesinContinuousCurrent

Mode,theshutdowntimeofprimaryswitchshouldbelargerthan24uS.

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SY52251

SO8Packageoutline&PCBlayoutdesign

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