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| 型号： | LTC4267IGN#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/32页 |
| 文件大小： | 0K |
| 描述： | IC POE 802.3AF INTERFACE 16SSOP |
| 标准包装： | 2,500 |
| 控制器类型： | 以太网供电控制器（POE） |
| 接口： | IEEE 802.3af |
| 电流 - 电源： | 3mA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SSOP |
| 包装： | 带卷 (TR) |
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LTC4267
16
4267fc
The undervoltage lockout mechanism on PVCC prevents
the LTC4267 switching regulator from trying to drive the
external N-Channel MOSFET with insufcient gate-to-
Adjustable Slope Compensation
The LTC4267 switching regulator injects a 5A peak cur-
rent ramp out through its SENSE pin which can be used
for slope compensation in designs that require it. This
current ramp is approximately linear and begins at zero
current at 6% duty cycle, reaching peak current at 80%
duty cycle. Programming the slope compensation via a
series resistor is discussed in the External Interface and
Component Selection section.
EXTERNAL INTERFACE AND COMPONENT SELECTION
Input Interface Transformer
Nodes on an Ethernet network commonly interface to the
outside world via an isolation transformer (Figure 9). For
PoE devices, the isolation transformer must include a
center tap on the media (cable) side. Proper termination
is required around the transformer to provide correct
impedance matching and to avoid radiated and conducted
emissions. Transformer vendors such as Bel Fuse, Coil-
craft, Pulse and Tyco (Table 3) can provide assistance with
selection of an appropriate isolation transformer and proper
termination methods. These vendors have transformers
specically designed for use in PD applications.
Table 3. Power over Ethernet Transformer Vendors
VENDOR
CONTACT INFORMATION
Bel Fuse Inc.
206 Van Vorst Street
Jersey City, NJ 07302
Tel: 201-432-0463
FAX: 201-432-9542
http://www.belfuse.com
Coilcraft, Inc.
1102 Silver Lake Road
Cary, IL 60013
Tel: 847-639-6400
FAX: 847-639-1469
http://www.coilcraft.com
Pulse Engineering
12220 World Trade Drive
San Diego, CA 92128
Tel: 858-674-8100
FAX: 858-674-8262
http://www.pulseeng.com
Tyco Electronics
308 Constitution Drive
Menlo Park, CA 94025-1164
Tel: 800-227-7040
FAX: 650-361-2508
http://www.circuitprotection.com
APPLICATIO S I FOR ATIO
WU
UU
Figure 8. LTC4267 Switching Regulator
Start-Up/Shutdown State Diagram
source voltage. The voltage at the PVCC pin must exceed
VTURNON (nominally 8.7V with respect to PGND) at least
momentarily to enable operation. The PVCC voltage must
fall to VTURNOFF (nominally 5.7V with respect to PGND)
before the undervoltage lockout disables the switching
regulator. This wide UVLO hysteresis range supports
applications where a bias winding on the yback trans-
former is used to increase the efciency of the LTC4267
switching regulator.
The ITH/RUN can be driven below VITHSHDN (nominally
0.28V with respect to PGND) to force the LTC4267 switching
regulator into shutdown. An internal 0.3A current source
always tries to pull the ITH/RUN pin towards PVCC. When
the ITH/RUN pin voltage is allowed to exceed VITHSHDN and
PVCC exceeds VTURNON, the LTC4267 switching regulator
begins to operate and an internal clamp immediately pulls
the ITH/RUN pin to about 0.7V. In operation, the ITH/RUN
pin voltage will vary from roughly 0.7V to 1.9V to represent
current comparator thresholds from zero to maximum.
Internal Soft-Start
An internal soft-start feature is enabled whenever the
LTC4267 switching regulator comes out of shutdown.
Specically, the ITH/RUN voltage is clamped and is
prevented from reaching maximum until 1.4ms have
passed. This allows the input current of the PD to rise in a
smooth and controlled manner on start-up and stay within
the current limit requirement of the LTC4267 interface.
LTC4267
PWM
SHUTDOWN
LTC4267
PWM
ENABLED
VITH/RUN
< VITHSHDN
(NOMINALLY
0.28V)
VITH/RUN > VITHSHDN
AND PVCC > VTURNON
(NOMINALLY 8.7V)
PVCC < VTURNOFF
4267 F08
ALL VOLTAGES WITH
RESPECT TO PGND
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4268-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller |
| LTC4268-1_12 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Power PD With Synchronous No-Opto Flyback Controller |
| LTC4268CDKD-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Power PD with Synchronous NoOpto Flyback Controller |
| LTC4268CDKD-1#PBF | 功能描述:IC PD HIGH POWER W/CNTRL 32-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 标准包装:50 系列:- 类型:热交换控制器 应用:-48V 远程电力系统，AdvancedTCA ? 系统，高可用性 内部开关:无 电流限制:可调 电源电压:11.5 V ~ 14.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-MSOP 包装:管件 |
| LTC4268CDKD-1#TRPBF | 功能描述:IC PD HIGH POWER W/CNTRL 32-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 标准包装:50 系列:- 类型:热交换控制器 应用:-48V 远程电力系统，AdvancedTCA ? 系统，高可用性 内部开关:无 电流限制:可调 电源电压:11.5 V ~ 14.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-MSOP 包装:管件 |
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