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| 型号： | SI3402-A-GMR |
| 厂商： | Silicon Laboratories Inc |
| 文件页数： | 12/22页 |
| 文件大小： | 0K |
| 描述： | IC POE PD LOW EMI SW REG 20VQFN |
| 标准包装： | 2,500 |
| 类型： | 以太网供电开关（PoE） |
| 应用： | IP 电话，LAN 网络供电，网络路由器和交换机 |
| 内部开关： | 是 |
| 电流限制： | 470mA |
| 电源电压： | 2.8 V ~ 57 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-VQFN 裸露焊盘 |
| 供应商设备封装： | 20-QFN（5x5） |
| 包装： | 带卷 (TR) |
Si3402
Table 10. Class Resistor Values
Class
Usage
Peak Power Levels
Nominal Class
RCL Resistor (1%,
Current
1/16 W)
0
Default
0.44 to 12.95 W
< 4 mA
> 1.33 k ?
(or open circuit)
1
2
3
4
Optional
Optional
Optional
PoE+
0.44 to 3.84 W
3.84 to 6.49 W
6.49 to 12.95 W
12.95 to 17 W
10.5 mA
18.5 mA
28 mA
40 mA
127 ?
69.8 ?
45.3 ?
30.9 ?
The 802.3 specification limits the classification time to
75 ms to limit the power dissipated in the PD. If the PSE
classification period exceeds 75 ms and the die
temperature rises above the thermal shutdown limits,
the thermal protection circuit will engage and disable
the classification current source in order to protect the
Si3402. The Si3402 stays in classification mode until
the input voltage exceeds 22 V (the upper end of its
classification operation region).
3.2.4. Under Voltage Lockout
The 802.3 standard specifies the PD to turn on when
the line voltage rises to 42 V and for the PD to turn off
when the line voltage falls to 30 V. The PD must also
maintain a large on-off hysteresis region to prevent
wiring losses between the PSE and the PD from
causing startup oscillation.
The Si3402 incorporates an undervoltage lockout
(UVLO) circuit to monitor the line voltage and determine
when to apply power to the integrated switching
regulator. Before the power is applied to the switching
regulator, the hotswap switch output (HSO) pin is high-
impedance and typically follows VPOS as the input is
ramped (due to the discharged switcher supply
capacitor). When the input voltage rises above the
UVLO turn-on threshold, the Si3402 begins to turn on
the internal hotswap power MOSFET. The switcher
supply capacitor begins to charge up under the current
limit control of the Si3402, and the HSO pin transitions
from VPOS to VNEG. The Si3402 includes hysteretic
UVLO circuits to maintain power to the load until the
input voltage falls below the UVLO turn-off threshold.
Once the input voltage falls below 30 V, the internal
hotswap MOSFET is turned off.
3.2.5. Dual Current Limit and Switcher Turn-On
The Si3402 implements dual current limits. While the
hotswap MOSFET is charging the switcher supply
capacitor, the Si3402 maintains a low current limit. The
switching regulator is disabled until the voltage across
the hotswap MOSFET becomes sufficiently low,
indicating the switcher supply capacitor is almost
completely charged. When this threshold is reached,
the switcher is activated, and the hotswap current limit
is increased. This threshold also has hysteresis to
prevent systemic oscillation as the switcher begins to
draw current and the current limit is increased, which
allows resistive losses in the cable to effectively
decrease the input supply.
The Si3402 stays in a high-level current limit mode until
the input voltage drops below the UVLO turn-off
threshold or excessive power is dissipated in the
hotswap switch. This dual level current limit allows the
system designer to design powered devices for use with
both legacy and compliant PoE systems.
An additional feature of the dual current limit circuitry is
foldback current limiting in the event of a fault condition.
When the current limit is switched to the higher level,
400 mA of current can be drawn by the PD. Should a
fault cause more than this current to be consumed, the
voltage across the hotswap MOSFET will increase to
clamp the maximum amount of power consumed. The
power dissipated by the MOSFET can be very high
under this condition. If the fault is very low impedance,
the voltage across the hotswap MOSFET will continue
to rise until the lower current limit level is engaged,
further reducing the dissipated power. If the fault
condition remains, the thermal overload protection
circuitry will eventually engage and shut down the
hotswap interface and switching regulator. The foldback
current limiting occurs much faster than the thermal
overload protection and is, therefore, necessary for
comprehensive protection of the hotswap MOSFET.
12
Rev. 1.31
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相关代理商/技术参数 |
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| SI3402B-EVB | 功能描述:Si3402-B - Special Purpose DC/DC, Power Over Ethernet 1, Non-Isolated Outputs Evaluation Board 制造商:silicon labs 系列:- 零件状态:新产品 主要用途:特殊用途 DC/DC，以太网供电（POE） 输出和类型:1，非隔离 功率 - 输出:- 电压 - 输出:5V 电流 - 输出:- 电压 - 输入:44 V ~ 57 V 稳压器拓扑:降压 频率 - 开关:350kHz 板类型:完全填充 所含物品:板 使用的 IC/零件:Si3402-B 标准包装:1 |
| SI3402-B-GM | 功能描述:IC POE PD LOW EMI SW REG 20VQFN 制造商:silicon labs 系列:- 包装:托盘 零件状态:在售 类型:控制器（PD），DC/DC 通道数:1 功率 - 最大值:17W 内部开关:是 辅助作用:无 标准:802.3at（PoE+），802.3af（PoE） 电压 - 电源:2.8 V ~ 57 V 电流 - 电源:2mA 工作温度:-40°C ~ 85°C 封装/外壳:20-VQFN 裸露焊盘 供应商器件封装:20-QFN（5x5） 标准包装:490 |
| SI3402-B-GMR | 功能描述:IC POE PD LOW EMI SW REG 20VQFN 制造商:silicon labs 系列:- 包装:剪切带（CT） 零件状态:在售 类型:控制器（PD），DC/DC 通道数:1 功率 - 最大值:17W 内部开关:是 辅助作用:无 标准:802.3at（PoE+），802.3af（PoE） 电压 - 电源:2.8 V ~ 57 V 电流 - 电源:2mA 工作温度:-40°C ~ 85°C 封装/外壳:20-VQFN 裸露焊盘 供应商器件封装:20-QFN（5x5） 标准包装:1 |
| SI3402BISO-EVB | 功能描述:Si3402-B - Special Purpose DC/DC, Power Over Ethernet 1, Isolated Outputs Evaluation Board 制造商:silicon labs 系列:- 零件状态:新产品 主要用途:特殊用途 DC/DC，以太网供电（POE） 输出和类型:1，隔离 功率 - 输出:- 电压 - 输出:5V 电流 - 输出:- 电压 - 输入:44 V ~ 57 V 稳压器拓扑:回扫 频率 - 开关:350kHz 板类型:完全填充 所含物品:板 使用的 IC/零件:Si3402-B 标准包装:1 |
| Si3402-EVB | 功能描述:电源管理IC开发工具 PoE Pwrd-Non-Isolatd Low-EMI Eval Board RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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