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參數(shù)資料
| 型號(hào)： | LTC4274AIUHF-4#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： | 7 X 5 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38 |
| 文件頁數(shù)： | 19/28頁 |
| 文件大小： | 313K |
| 代理商： | LTC4274AIUHF-4#TRPBF |
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LTC4274A/LTC4274C
26
4274acf
External MOSFET
CarefulselectionofthepowerMOSFETiscriticaltosystem
reliability. LTC recommends either Fairchild IRFM120A,
FDT3612, FDMC3612 or Philips PHT6NQ10T for their
proven reliability in Type 1 and Type 2 PSE applications.
Non-standard applications that provide more current than
the 850mA IEEE maximum may require heat sinking and
other MOSFET design considerations. Contact LTC Ap-
plications before using a MOSFET other than one of these
recommended parts.
Sense Resistor
TheLTC4274A/LTC4274Cisdesignedtouseeither0.5Ωor
0.25Ω current sense resistors. For new designs 0.25Ω is
recommended to reduce power dissipation; the 0.5Ω op-
tion is intended for existing systems where the LTC4274A/
LTC4274Cisusedasadrop-inreplacementfortheLTC4258
or LTC4259A. The lower sense resistor values reduce
heat dissipation. Four commonly available 1Ω resistors
(0402 or larger package size) can be used in parallel in
place of a single 0.25Ω resistor. In order to meet the ICUT
and ILIM accuracy required by the IEEE specification, the
sense resistors should have ±1% tolerance or better, and
no more than ±200ppm/°C temperature coefficient.
Port Output Cap
The port requires a 0.22μF cap across its output to keep
the LTC4274A/LTC4274C stable while in current limit
during startup or overload. Common ceramic capacitors
often have significant voltage coefficients; this means the
capacitance is reduced as the applied voltage increases.
To minimize this problem, X7R ceramic capacitors rated
for at least 100V are recommended.
ESD/Cable Discharge Protection
EthernetportscanbesubjecttosignificantESDeventswhen
long data cables, each potentially charged to thousands
of volts, are plugged into the low impedance of the RJ45
jack. To protect against damage, the port requires a pair
of clamp diodes; one to AGND and one to VEE (Figure 10).
An additional surge suppressor is required for each
LTC4274A/LTC4274C chip from VEE to AGND. The diodes
at the port steer harmful surges into the supply rails,
where they are absorbed by the surge suppressor and the
VEE bypass capacitance. The surge suppressor has the
additional benefit of protecting the LTC4274A/LTC4274C
from transients on the VEE supply.
S1B diodes work well as port clamp diodes, and an
SMAJ58A or equivalent is recommended for the VEEsurge
suppressor.
LAYOUT GUIDELINES
Strict adherence to board layout, parts placement and
routing guidelines is critical for optimal current read-
ing accuracy, IEEE compliance, system robustness, and
thermal dissipation.
Power delivery above 25.5W imposes additional com-
ponent and layout restraints. Specifically MOSFET, sense
resistor and transformer selection is crucial to safe and
reliable system operation.
Contact LTC Applications to obtain a full set of layout
guidelines, example layouts and BOMs.
ApplicAtions inForMAtion
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC4274C | 制造商:LINER 制造商全稱:Linear Technology 功能描述:12-Port PoE/PoE+/LTPoE++ PSE Controller |
| LTC4274CIUHF#PBF | 功能描述:IC CONTROLLER POE 38-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:119 系列:- 類型:熱交換控制器 應(yīng)用:通用型，PCI Express? 內(nèi)部開關(guān):無 電流限制:- 電源電壓:3.3V，12V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:80-TQFP 供應(yīng)商設(shè)備封裝:80-TQFP（12x12） 包裝:托盤 產(chǎn)品目錄頁面:1423 (CN2011-ZH PDF) |
| LTC4274CIUHF#TRPBF | 功能描述:IC CONTROLLER POE 38-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:119 系列:- 類型:熱交換控制器 應(yīng)用:通用型，PCI Express? 內(nèi)部開關(guān):無 電流限制:- 電源電壓:3.3V，12V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:80-TQFP 供應(yīng)商設(shè)備封裝:80-TQFP（12x12） 包裝:托盤 產(chǎn)品目錄頁面:1423 (CN2011-ZH PDF) |
| LTC4274CUHF#PBF | 功能描述:IC CONTROLLER POE 38-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:119 系列:- 類型:熱交換控制器 應(yīng)用:通用型，PCI Express? 內(nèi)部開關(guān):無 電流限制:- 電源電壓:3.3V，12V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:80-TQFP 供應(yīng)商設(shè)備封裝:80-TQFP（12x12） 包裝:托盤 產(chǎn)品目錄頁面:1423 (CN2011-ZH PDF) |
| LTC4274CUHF#TRPBF | 制造商:Linear Technology 功能描述:POE Controller 25.5W 38-Pin QFN EP |
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