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參數(shù)資料
| 型號： | TPS2376DDAR-H |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 電源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封裝： | GREEN, PLASTIC, POWER PAD, SOIC-8 |
| 文件頁數(shù)： | 4/23頁 |
| 文件大?。?/td> | 640K |
| 代理商： | TPS2376DDAR-H |
www.ti.com
DC/DC CONVERTER STARTUP
AUXILIARY POWER SOURCE ORING
SLVS646A – SEPTEMBER 2006 – REVISED SEPTEMBER 2006
APPLICATION INFORMATION (continued)
The PG pin can be left open if it is not used.
The PSE and TPS2376-H are power and current limited sources, which imposes certain constraints on the PD
power supply design. Improper design of the system can prevent PD startup with some combinations of Ethernet
lines and PSE sources. The root of most startup problems revolves around the dc/dc converter.
Dc/dc converters have a constant input power characteristic that causes them to draw high currents at low
voltage. Also, a converter may draw in excess of 125% of its rated power during startup when the output voltage
approaches its regulated value, and the output capacitors are charging while the load draws its full power. These
characteristics lead to two undesired events. First, if the converter starts up during inrush, it can draw more
current than available from the TPS2376-H and cause the startup cycle to fail. Second, if the converter startup
current exceeds the TPS2376-H current limit, it may discharge the bulk capacitor until V(RTN-VSS) exceeds 10 V
and forces the TPS2376-H into inrush.
The following guidelines should be used:
1. Set the TPS2376-H inrush to a moderate value such as 140 mA.
2. Hold the dc/dc converter off during inrush using PG.
3. Implement a softstart that keeps the peak start-up current below 600 mA, and preferably only a modest
amount over the operating current, at the minimum PSE voltage and maximum feed resistance.
4. If step 3 cannot be met, the bulk input capacitor should not discharge more than 8 V during start-up at the
minimum PSE voltage and maximum feed resistance. 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, it is always a good practice to follow them.
Downstream converters that use PG control are turned off during a hard fault or thermal cycle, and will go
through an orderly restart once the bulk capacitor is recharged. Converters that do not use PG need to permit a
restart by either drawing less current than the inrush current limit provides, or by disabling long enough to allow
the bulk capacitor to recharge. A converter that has bootstrap startup can be designed to accomplish this goal.
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 14 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 TPS2376-H output. Option 3 applies power to the TPS2376-H 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.
12
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參數(shù)描述 |
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| TPS2376DDAR-HG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Hi Pwr PD CONTROLLER RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| TPS2376DG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| TPS2376DR | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| TPS2376DRG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| TPS2376HEVM | 功能描述:電源管理IC開發(fā)工具 TPS2376H Evaluation Module RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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