參數(shù)資料
型號： LTC4266CUHF#PBF
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)： 19/30頁
文件大?。?/td> 414K
代理商： LTC4266CUHF#PBF
LTC4266
4266fa
OutputCap
Eachportrequiresa0.22μFcapacrossitsoutputstokeep
theLTC4266stablewhileincurrentlimitduringstartup
oroverload.Commonceramiccapacitorsoftenhavesig-
nificantvoltagecoefficients;thismeansthecapacitance
isreducedastheappliedvoltageincreases.Tominimize
thisproblem,X7Rceramiccapacitorsratedforatleast
100Varerecommended.
ESD/CableDischargeProtection
EthernetportscanbesubjecttosignificantESDevents
whenlongdatacables,eachpotentiallychargedtothou-
sandsofvolts,arepluggedintothelowimpedanceofthe
RJ45jack.Toprotectagainstdamage,eachportrequiresa
pairofclampdiodes;onetoAGNDandonetoVEE(Figure
10).Anadditionalsurgesuppressorisrequiredforeach
LTC4266chipfromVEEtoAGND.Thediodesattheports
steerharmfulsurgesintothesupplyrails,wheretheyare
absorbedbythesurgesuppressorandtheVEEbypass
capacitance. The surge suppressor has the additional
benefitofprotectingtheLTC4266fromtransientsonthe
VEEsupply.
S1B diodes work well as port clamp diodes, and an
SMAJ58AorequivalentisrecommendedfortheVEEsurge
suppressor.
LAYOUTGUIDELINES
StandardpowerlayoutguidelinesapplytotheLTC4266:
placethedecouplingcapsfortheVDDandVEEsupplies
neartheirrespectivesupplypins,usegroundplanes,and
usewidetraceswherevertherearesignificantcurrents.
Themainlayoutchallengeinvolvesthearrangementof
the current sense resistors, and their connections to
theLTC4266.Becausethesenseresistorvaluesarevery
low,layoutparasiticscancausesignificanterrors.Careis
requiredtoachievespecifiedaccuracy,particularlywith
disconnectcurrents.
Figure19illustratestheproblem.Intheexampleonthe
left,twoportshaveloadcurrentsI1andI2thatreturnto
theVEEpowersupplythroughamutualresistanceRM.
RMrepresentsthecombinedresistancesofanytraces,
planes,andviasinthePCBthatI1andI2shareasthey
returntotheVEEsupply.TheLTC4266measuresthevolt-
agedifferencebetweenitsSENSEandVEEpinstosense
thevoltagedropacrossRS1,butastheexampleshows,
RMintroduceserrors.
The example on the right shows how errors can be
minimizedwithagoodlayout.Thecircuitisrearranged
sothatRMnolongeraffectsVS,andtheVEEconnection
totheLTC4266isusedasaKelvinsensetrace.VEEisnot
aperfectKelvinconnectionbecauseallfourportscon-
trolledbytheLTC4266sharethesamesensetrace,and
becausethecurrentthroughthetrace(IEE)isnotzero.
However,astheequationshows,theremainingerrorisa
smalloffsetterm.
Figure20showstwoLTC4266chipscontrollingeightports
(AthoughH).Theportsareseparatedintotwogroups
offour;eachhasitsowntraceonthetopPCBlayerthat
ApplicAtions inForMAtion
RM
+
VS
+
VS
RS1
MUTUAL RESISTANCE
RS2
4266 F19
IEE
–
I1 I2
I1 + I2 + IEE
VS = I1RS1 + I1RM + I2RM
LTC4266
GATE
SENSE
SIGNAL
SCALE ERROR
CROSSTALK ERROR
VEE
RK
RM
RS1
KELVIN SENSE LINE
RS2
IEE
I1 I2
VS = I1RS1 – IEERK
I1 + I2 + IEE
LTC4266
GATE
SENSE
SIGNAL
SMALL OFFSET ERROR
VEE
Figure19.LayoutAffectsCurrentReadbackAccuracy
相關PDF資料
PDF描述
LTC500-4MM LOW PASS FILTER
LTC6603CUF#PBF LOW PASS FILTER
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LTC6603IUF#TRPBF LOW PASS FILTER
相關代理商/技術參數(shù)
參數(shù)描述
LTC4266IGW#PBF 功能描述:IC CTRLR IEEE 802.3AT 36-SSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 控制器 系列:- 標準包裝: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 供應商設備封裝:24-HVQFN（4x4） 包裝:托盤 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名稱:935286452157SC18IS600IBSSC18IS600IBS-ND
LTC4266IGW#TRPBF 制造商:Linear Technology 功能描述:Power Over Ethernet Controller 36-Pin SSOP W T/R 制造商:Linear Technology 功能描述:MS-Hot Swap/POE, PoE+ 25.5W Quad PSE Controller
LTC4266IUHF#PBF 制造商:Linear Technology 功能描述:POE Controller 25.5W 38-Pin QFN EP 制造商:Linear Technology 功能描述:IC POE 802.3AT QUAD PSE 38-QFN 制造商:Linear Technology 功能描述:POE CNTRL QUAD 25.5W 1MHZ 制造商:Linear Technology 功能描述:IC, POE CONTROLLER, 3.3V, QFN-38; Input Voltage:3.3V; Supply Current:-2.4mA; UVLO:25V; Digital IC Case Style:QFN; No. of Pins:38; Frequency:1MHz; Operating Temperature Min:-40C; Operating Temperature Max:85C; MSL:MSL 1 - Unlimited ;RoHS Compliant: Yes
LTC4266IUHF#TRPBF 制造商:Linear Technology 功能描述:POE Controller 25.5W 38-Pin QFN EP
LTC4267 制造商:LINER 制造商全稱:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller
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