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参数资料
| 型号： | LTC4274AIUHF-3#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： | 7 X 5 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38 |
| 文件页数： | 17/28页 |
| 文件大小： | 313K |
| 代理商： | LTC4274AIUHF-3#PBF |
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LTC4274A/LTC4274C
24
4274acf
ApplicAtions inForMAtion
VEE is the main supply that provides power to the PD.
Because it supplies a relatively large amount of power and
issubjecttosignificantcurrenttransients,itrequiresmore
design care than a simple logic supply. For minimum IR
loss and best system efficiency, set VEE near maximum
amplitude (57V), leaving enough margin to account for
transient over- or undershoot, temperature drift, and the
line regulation specs of the particular power supply used.
Bypass capacitance between AGND and VEE is very impor-
tant for reliable operation. If a short-circuit occurs at the
output port it can take as long as 1μs for the LTC4274A/
LTC4274C to begin regulating the current. During this
time the current is limited only by the small impedances
in the circuit and a high current spike typically occurs,
causing a voltage transient on the VEE supply and possibly
causing the LTC4274A/LTC4274C to reset due to a UVLO
fault. A 1μF, 100V X7R capacitor placed near the VEE pin
is recommended to minimize spurious resets.
Isolating the Serial Bus
The LTC4274A/LTC4274C includes a split SDA pin (SDAIN
and SDAOUT) to ease opto-isolation of the bidirectional
SDA line.
IEEE 802.3 Ethernet specifications require that network
segments (including PoE circuitry) be electrically isolated
from the chassis ground of each network interface device.
However,networksegmentsarenotrequiredtobeisolated
fromeachother,providedthatthesegmentsareconnected
to devices residing within a single building on a single
power distribution system.
For simple devices such as small PoE switches, the isola-
tion requirement can be met by using an isolated main
power supply for the entire device. This strategy can be
used if the device has no electrically conducting ports
other than twisted-pair Ethernet. In this case, the SDAIN
and SDAOUT pins can be tied together and will act as a
standard I2C/SMBus SDA pin.
If the device is part of a larger system, contains additional
external non-Ethernet ports, or must be referenced to
protective ground for some other reason, the Power over
Ethernet subsystem (including all LTC4274A/LTC4274Cs)
must be electrically isolated from the rest of the system.
Figure 16 shows a typical isolated serial interface. The
SDAOUT pin of the LTC4274A/LTC4274C is designed to
drive the inputs of an opto-coupler directly. Standard I2C/
SMBusdevicestypicallycannotdriveopto-couplers,soU1
is used to buffer the signals from the host controller side.
Figure 15. Positive VDD Boost Converter
4274AC F15
R54
56k
C79
2200pF
GND
ITH/RUN
LTC3803
VCC
2
5
VFB
1
3
NGATE
Q15
FDC2512
Q13
FMMT723
Q14
FMMT723
SENSE
6
4
VEE
C74
100F
6.3V
C75
10F
16V
L3
100H
SUMIDA CDRH5D28-101NC
R51
4.7k
1%
R53
4.7k
1%
R52
3.32k
1%
3.3V AT 400mA
R55
806
1%
R59
0.100
1%, 1W
R56
47.5k
1%
R57
1k
D28
B1100
R58
10
R60
10
C73
10F
6.3V
L4
10H
SUMIDA CDRH4D28-100NC
+
C77
0.22F
100V
C78
0.22F
100V
C76
10F
63V
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相关代理商/技术参数 |
参数描述 |
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| LTC4274AIUHF-4#PBF | 功能描述:IC CONTROLLER POE 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4274AIUHF-4#TRPBF | 功能描述:IC CONTROLLER POE 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4274C | 制造商:LINER 制造商全称: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 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4274CIUHF#TRPBF | 功能描述:IC CONTROLLER POE 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
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