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| 型号： | TPS2376PWG4 |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封装： | GREEN, PLASTIC, TSSOP-8 |
| 文件页数： | 6/24页 |
| 文件大小： | 579K |
| 代理商： | TPS2376PWG4 |
POWER SYSTEM DESIGN
AUXILIARY POWER SOURCE ORING
TPS237X
SMAJ58A
R(DET)
R(CLASS)
VDD
VSS
CLASS
DET
RTN
Main
DC/DC
Converter
Output
R(ILIM)
RJ45
Option 1
ILIM
DC/DC
Converter
UCC3809
or
UCC3813
Optional
Regulator
Option 2
Option 3
A Full Wave Bridge
Gives Flexibility To
Use Supply With Either
Polarity
For Option 2,
The Capacitor Must Be
Right At The Output
To Control The
Transients.
Auxiliary
Power
Input
Use only
one option
See TI Document SLVR030 For A Typical
Application Circuit.
~
+
~
+
0.1
F
22
F
Inserting a Diode in This Location
With Option 2, Allows PoE To Start
With Aux Power Present.
data sheet
SLVS525B – APRIL 2004 – REVISED APRIL 2008............................................................................................................................................................ www.ti.com
The PSE is a power and current limited source, which imposes certain constraints on the PD power supply
design. DC/DC converters have both a constant input power characteristic that causes them to draw high
currents at low voltage, and they tend to go to a full input power mode during start-up that is often 25% or more
above their rated power. Improper design of the power system can cause the PD to not start up with all
combinations of Ethernet lines and PSE sources.
The following guidelines should be used:
1. Set the TPS2375 inrush to a moderate value as previously discussed.
2. Hold the dc/dc converter off during inrush as previously discussed.
3. The converter should have a softstart that keeps the peak input start-up current below 400 mA, and
preferably only a modest amount over the operating current, with a 44-V PSE source and a 20-
loop.
4. If step 3 cannot be met, the bulk input capacitor should not discharge more than 8 V during converter start
up from a 400-mA limited, 44-V source with a 20-
line. Start-up must be completed in less than 50 mS
Step 4 requires a balance between the converter output capacitance, load, and input bulk capacitance. While
there are some cases which may not require all these measures, such as a 1-W PD with minimal converter
output capacitance, it is always a good practice to follow them.
Many PoE capable devices are designed to operate from either a wall adapter or PoE power. A local power
solution adds cost and complexity, but allows a product to be used regardless of PoE availability. Attempting to
create solutions where the two power sources coexist in a specific controlled manner results in additional
complexity, and is not generally recommended. Figure 21 demonstrates three methods of diode ORing external
power into a PD. Option 1 inserts power on the output side of the PoE power conversion. Option 2 inserts power
on the TPS2375 output. Option 3 applies power to the TPS2375 input. Each of these options has advantages
and disadvantages. The wall adapter must meet a minimum 1500-Vac dielectric withstand test voltage to the ac
input power and to ground for options 2 and 3.
Figure 21. Auxiliary Power ORing
14
Copyright 2004–2008, Texas Instruments Incorporated
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS2376PWR | 功能描述:热插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| TPS2376PWRG4 | 功能描述:热插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| TPS23770PWP | 功能描述:热插拔功率分布 IEEE 802.3af PD Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| TPS23770PWPG4 | 功能描述:热插拔功率分布 IEEE 802.3af PD Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| TPS23770PWPR | 功能描述:热插拔功率分布 IEEE 802.3af PD Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
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