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参数资料
| 型号： | LTC4257CS8-1#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | IEEE 802.3af PD Power over Ethernet Interface Controller; Package: SO; No of Pins: 8; Temperature Range: 0°C to +70°C |
| 中文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SO-8 |
| 文件页数： | 20/20页 |
| 文件大小： | 265K |
| 代理商： | LTC4257CS8-1#PBF |
LTC4257-1
9
42571fb
specification. The LTC4257-1 is compatible with the IEEE
802.3af standard and also works with the obsolete Mea-
sured Voltage method.
In the Measured Current method (Figure 4), the PSE
presents a fixed voltage between –15.5V and –20.5V to the
PD. With the input voltage in this range, the LTC4257-1
asserts a load current from the GND pin through the
RCLASS resistor. The magnitude of the load current is set
with the selection of the RCLASS resistor. The resistor value
associated with each class is shown in Table 2.
In the Measured Voltage method (Figure 5), the PSE drives
a current into the PD and monitors the voltage across the
PD terminals. The PSE current steps between classifica-
tion load current values in order to classify the PD under
test. For PSE probe currents below the PD load current, the
LTC4257-1 will keep the PD terminal voltage below the
classification voltage range. For PSE probe currents above
the PD load current, the LTC4257-1 will force the PD
terminal voltage above the classification voltage range.
During classification, a moderate amount of power is
dissipated in the LTC4257-1. The IEEE 802.3af specifica-
tion limits the classification time to 75ms. The LTC4257-1
is designed to handle the power dissipation for this time
period. If the PSE probing exceeds 75ms, the LTC4257-1
may overheat. In this situation, the thermal protection
circuit will engage and disable the classification current
source in order to protect the part. The LTC4257-1 stays
in classification mode until the input voltage rises above
the UVLO turn-on voltage.
APPLICATIO S I FOR ATIO
WU
UU
Figure 5. IEEE 802.af Measured-Voltage Method
of Classification Probing
GND
RCLASS
VIN
8
2
4
LTC4257-1
CONSTANT
LOAD
CURRENT
INTERNAL
TO LTC4257-1
42571 F05
RCLASS
CURRENT PATH
V
PD
PSE
VOLTAGE
MONITOR
PSE
PROBING
CURRENT
SOURCE
IF PSE PROBING CURRENT < LTC4257-1 LOAD CURRENT, PD TERMINAL VOLTAGE IS < 15V
IF PSE PROBING CURRENT > LTC4257-1 LOAD CURRENT, PD TERMINAL VOLTAGE IS > 20V
GND
RCLASS
VIN
8
2
4
LTC4257-1
CONSTANT
LOAD
CURRENT
INTERNAL
TO LTC4257-1
42571 F04
RCLASS
CURRENT PATH
V
PD
PSE
PSE CURRENT MONITOR
PSE
PROBING
VOLTAGE
SOURCE
–15.5V TO –20.5V
Figure 4. IEEE 802.3af Measured-Current Method
of Classification Probing
相关PDF资料 |
PDF描述 |
|---|---|
| LTC4257CS8-1#TRPBF | IEEE 802.3af PD Power over Ethernet Interface Controller; Package: SO; No of Pins: 8; Temperature Range: 0°C to +70°C |
| LTC4257IDD-1#PBF | IEEE 802.3af PD Power over Ethernet Interface Controller; Package: DFN; No of Pins: 8; Temperature Range: -40°C to +85°C |
| LTC4257IDD-1#TRPBF | IEEE 802.3af PD Power over Ethernet Interface Controller; Package: DFN; No of Pins: 8; Temperature Range: -40°C to +85°C |
| LTC4257IS8-1#PBF | IEEE 802.3af PD Power over Ethernet Interface Controller; Package: SO; No of Pins: 8; Temperature Range: -40°C to +85°C |
| LTC4257IS8-1#TRPBF | IEEE 802.3af PD Power over Ethernet Interface Controller; Package: SO; No of Pins: 8; Temperature Range: -40°C to +85°C |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4257IDD | 功能描述:IC CONTROLLER POE INTERFACE 8DFN RoHS:否 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 |
| LTC4257IDD#PBF | 功能描述:IC CONTROLLER POE INTERFACE 8DFN 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 |
| LTC4257IDD#TR | 功能描述:IC CONTROLLER POE INTERFACE 8DFN RoHS:否 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 |
| LTC4257IDD#TRPBF | 功能描述:IC CONTROLLER POE INTERFACE 8DFN 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 |
| LTC4257IDD-1 | 功能描述:IC CONTROLLER POE INTERFACE 8DFN RoHS:否 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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