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参数资料
| 型号： | LTC4268IDKD-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/46页 |
| 文件大小： | 419K |
| 描述： | IC PD HIGH POWER W/CNTRL 32-DFN |
| 标准包装： | 2,500 |
| 类型： | 以太网供电开关（PoE） |
| 应用： | 远程外设（工业控制，相机，数据访问） |
| 内部开关： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFDFN 裸露焊盘 |
| 供应商设备封装： | 32-DFN（7x4）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC4268-1
16
42681fc
applicaTions inForMaTion
classification for use in closed systems and is not defined
or supported by the IEEE 802.3af. With the extended clas-
sification range available in the LTC4268-1, it is possible
for system designers to define multiple classes using load
currents between 40mA and 75mA.
During classification, the PSE presents a fixed voltage
between 15.5V and 20.5V to the PD (Figure 5). With the
input voltage in this range, the LTC4268-1 asserts a load
current from the V
PORTP
pin through the R
CLASS
resistor.
The magnitude of the load current is set with the selection
of the R
CLASS
resistor. The resistor value associated with
each class is shown in Table 2.
A substantial amount of power is dissipated in the
LTC4268-1 during classification. The IEEE 802.3af specifi-
cation limits the classification time to 75ms in order avoid
excessive heating. The LTC4268-1 is designed to handle
the power dissipation during the probe period. If the PSE
probing exceeds 75ms, the LTC4268-1 may overheat. In
this situation, the thermal protection circuit will engage
and disable the classification current source, protecting
the LTC4268-1 from damage. When the die cools, clas-
sification is automatically resumed.
Classification presents a challenging stability problem
for the
PSE due to the wide range of loads possible. The
LTC4268-1 has been designed to avoid PSE interoperability
problems by maintaining a positive I-V slope throughout
the signature and classification ranges up to UVLO turn
on as shown in Figure 6. The positive I-V slope avoids
areas of negative resistance and helps prevent the PSE
from power cycling or getting stuck during signature
or classification probing. In the event a PSE overshoots
beyond the classification voltage range, the available load
current aids in returning the PD back into the classification
voltage range. (The PD input may otherwise be trapped
by a reverse-biased diode bridge and the voltage held by
the 0.1礔 capacitor.) By gently ramping the classification
current on and maintaining a positive I-V slope until UVLO
turn-on, the LTC4268-1 provides a well behaved load,
assuring interoperability with any PSE.
V
PORTP
R
CLASS
V
PORTN
LTC4268-1
CONSTANT
LOAD
CURRENT
INTERNAL
TO LTC4268-1
42681 F05
R
CLASS
CURRENT PATH
V
PD
PSE
PSE CURRENT MONITOR
PSE
PROBING
VOLTAGE
SOURCE
15.5V TO 20.5V
V
PORT
(V)
0
40
42681 F06
10
20
30
Figure 5. PSE Probing PD During Classification
Figure 6. LTC4268-1 Positive I-V Slope
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4269-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:IEEE 802.3at PD with Synchronous No-Opto Flyback Controller |
| LTC4269-2 | 制造商:LINER 制造商全称:Linear Technology 功能描述:IEEE 802.3at High Power PD and Synchronous Forward Controller with AUX Support |
| LTC4269CDKD-1#PBF | 功能描述:IC PD/OPTO FLYBACK CTRLR 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 |
| LTC4269CDKD-1#TRPBF | 功能描述:IC PD/OPTO FLYBACK CTRLR 32-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:100 系列:- 类型:热插拔开关 应用:通用 内部开关:是 电流限制:可调 电源电压:9 V ~ 13.2 V 工作温度:-40°C ~ 150°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN-EP（3x3） 包装:管件 |
| LTC4269CDKD-1-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:IEEE 802.3at PD with Synchronous No-Opto Flyback Controller |
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