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参数资料
| 型号： | LTC4266IUHF#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | POWER SUPPLY MANAGEMENT CKT, PQCC38 |
| 封装： | 5 X 7 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38 |
| 文件页数： | 19/30页 |
| 文件大小： | 414K |
| 代理商： | LTC4266IUHF#PBF |
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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
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4267 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller |
| LTC4267-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator |
| LTC4267-3 | 制造商:LINER 制造商全称: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 类别:集成电路 (IC) >> 接口 - 控制器 系列:- 标准包装:2,450 系列:- 控制器类型:SPI 总线至 I²C 总线桥接 接口:I²C，串行，SPI 电源电压:2.4 V ~ 3.6 V 电流 - 电源:11mA 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘 供应商设备封装:24-HVQFN（4x4） 包装:托盘 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名称:935286452157SC18IS600IBSSC18IS600IBS-ND |
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