參數(shù)資料
型號： LTC4266IUHF#TRPBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 電源管理
英文描述： POWER SUPPLY MANAGEMENT CKT, PQCC38
封裝： 5 X 7 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38
文件頁數(shù)： 13/30頁
文件大小： 414K
代理商： LTC4266IUHF#TRPBF
LTC4266
0
4266fa
ApplicAtions inForMAtion
powerstatusregistertoindicatethatitranthesecond
classificationcycle.ThesecondcyclealertsthePDthat
itisconnectedtoaType2PSEwhichcansupplyType2
powerlevels.
2-eventping-pongclassificationisenabledbysettingabit
intheport’shighpowermoderegister.Notethataping-
pongenabledportonlyrunsthesecondclassificationcycle
whenitdetectsaClass4device;ifthefirstcyclereturns
Class0to3,theportassumesitisconnectedtoaType1
PDanddoesnotrunthesecondclassificationcycle.
InvalidType2ClassCombinations
The802.3atspecdefinesaType2PDclasssignatureas
twoconsecutiveClass4results;aClass4followedby
aClass0-3isnotavalidsignature.Inautomode,the
LTC4266willpoweradetectedPDregardlessoftheclas-
sificationresults,withoneexception:ifthePDpresents
aninvalidType2signature(Class4followedbyClass0
to3),theLTC4266willnotprovidepowerandwillrestart
thedetectionprocess.Toaidindiagnosis,theportstatus
registerwillalwaysreporttheresultsofthelastclasspulse,
soaninvalidClass4–Class2combinationwouldreport
asecondclasspulsewasrunintheHighPowerStatus
register(whichimpliesthatthefirstcyclefoundClass4),
andClass2intheportstatusregister.
POWERCONTROL
ExternalMOSFET,SenseRSummary
The primary function of the LTC4266 is to control the
deliveryofpowertothePSEport.Itdoesthisbycontrol-
lingthegatedrivevoltageofanexternalpowerMOSFET
whilemonitoringthecurrentviaanexternalsenseresis-
torandtheoutputvoltageattheOUTpin.Thiscircuitry
servestocoupletherawVEEinputsupplytotheportin
acontrolledmannerthatsatisfiesthePD’spowerneeds
whileminimizingpowerdissipationintheMOSFETand
disturbancesontheVEEbackplane.
TheLTC4266isdesignedtouse0.25senseresistorsto
minimizepowerdissipation.Italsosupports0.5sense
resistors,whicharethedefaultwhenLTC4258/LTC4259A
compatibilityisdesired.
InrushControl
Oncethecommandhasbeengiventoturnonaport,the
LTC4266rampsuptheGATEpinofthatport’sexternal
MOSFETinacontrolledmanner.Undernormalpower-up
circumstances,theMOSFETgatewillriseuntiltheport
currentreachestheinrushcurrentlimitlevel(typically
450mA),atwhichpointtheGATEpinwillbeservoedto
maintainthespecifiedIINRUSHcurrent.Duringthisinrush
period,atimer(tSTART)runs.Whenoutputchargingis
complete,theportcurrentwillfallandtheGATEpinwill
beallowedtocontinuerisingtofullyenhancetheMOSFET
andminimizeitson-resistance.ThefinalVGSisnominally
13V.IfthetSTARTtimerexpiresbeforetheinrushperiod
completes,theportwillbeturnedbackoffandatSTART
faultreported.
CurrentLimit
EachLTC4266portincludestwocurrentlimitingthresholds
(ICUTandILIM),eachwithacorrespondingtimer(tCUT
andtLIM).SettingtheICUTandILIMthresholdsdepends
onseveralfactors:theclassofthePD,thevoltageofthe
mainsupply(VEE),thetypeofPSE(1or2),thesense
resistor(0.5Ωor0.25Ω),theSOAoftheMOSFET,and
whetherornotthesystemisrequiredtoimplementclass
enforcement.
PertheIEEEspec,theLTC4266willallowtheportcur-
renttoexceedICUTforalimitedperiodoftimebefore
removingpowerfromtheport,whereasitwillactively
controltheMOSFETgatedrivetokeeptheportcurrent
belowILIM.Theportdoesnottakeanyactiontolimitthe
current when only the ICUTthresholdisexceeded,but
doesstartthetCUTtimer.ThetLIMtimerstartswhenthe
ILIMthresholdisexceededandcurrentlimitisactive.If
thecurrentdropsbelowtheICUTcurrentthresholdbefore
itstimerexpires,thetCUTtimercountsbackdown,but
at1/16theratethatitcountsup.Thisallowsthecurrent
limitcircuitrytotolerateintermittentoverloadsignalswith
dutycyclesbelowabout6%;longerdutycycleoverloads
willturntheportoff.
ICUTistypicallysettoalowervaluethanILIMtoallowthe
porttotolerateminorfaultswithoutcurrentlimiting.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC4267 制造商:LINER 制造商全稱:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller
LTC4267-1 制造商:LINER 制造商全稱:Linear Technology 功能描述:Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator
LTC4267-3 制造商:LINER 制造商全稱:Linear Technology 功能描述:Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator
LTC4267CDHC 制造商:Linear Technology 功能描述:Hot Swap Controller 1-CH -57V 16-Pin DFN EP
LTC4267CDHC#PBF 功能描述:IC POE 802.3AF INTERFACE 16-DFN RoHS:是 類別:集成電路 (IC) >> 接口 - 控制器 系列:- 標(biāo)準(zhǔn)包裝:2,450 系列:- 控制器類型:SPI 總線至 I²C 總線橋接 接口:I²C，串行，SPI 電源電壓:2.4 V ~ 3.6 V 電流 - 電源:11mA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:24-HVQFN（4x4） 包裝:托盤 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名稱:935286452157SC18IS600IBSSC18IS600IBS-ND
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