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參數(shù)資料
| 型號(hào)： | TPS23754PWP |
| 廠(chǎng)商： | TEXAS INSTRUMENTS INC |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | 1.1 A SWITCHING CONTROLLER, 278 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | GREEN, PLASTIC, HTSSOP-20 |
| 文件頁(yè)數(shù)： | 8/41頁(yè) |
| 文件大小： | 1405K |
| 代理商： | TPS23754PWP |
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TPS23754
TPS23754-1
TPS23756
SLVS885D – OCTOBER 2008 – REVISED DECEMBER 2009
www.ti.com
DETAILED DESCRIPTION
PoE OVERVIEW
The following text is intended as an aid in understanding the operation of the TPS23754 but not as a substitute
for the IEEE 802.3at standard. The IEEE 802.3at standard is an update to IEEE 802.3-2008 clause 33 (PoE),
adding high-power options and enhanced classification. Generally speaking, a device compliant to IEEE
802.3-2008 is referred to as a type 1 device, and devices with high power and enhanced classification will be
referred to as type 2 devices. Standards change and should always be referenced when making design
decisions.
The IEEE 802.3at standard defines a method of safely powering a PD (powered device) over a cable by power
sourcing equipment (PSE), and then removing power if a PD is disconnected. The process proceeds through an
idle state and three operational states of detection, classification, and operation. The PSE leaves the cable
unpowered (idle state) while it periodically looks to see if something has been plugged in; this is referred to as
detection. The low power levels used during detection are unlikely to damage devices not designed for PoE. If a
valid PD signature is present, the PSE my inquire how much power the PD requires; this is referred to as
classification. The PSE may then power the PD if it has adequate capacity.
Type 2 PSEs are required to do type 1 hardware classification plus a (new) data-layer classification, or an
enhanced type 2 hardware classification. Type 1 PSEs are not required to do hardware or data link layer (DLL)
classification. A type 2 PD must do type 2 hardware classification as well as DLL classification. The PD may
return the default, 13W current-encoded class, or one of four other choices. DLL classification occurs after
power-on and the ethernet data link has been established.
Once started, the PD must present the maintain power signature (MPS) to assure the PSE that it is still present.
The PSE monitors its output for a valid MPS, and turns the port off if it loses the MPS. Loss of the MPS returns
the PSE to the idle state. Figure 21 shows the operational states as a function of PD input voltage. The upper
half is for IEEE 802.3-2008, and the lower half shows specific differences for IEEE 802.3at. The dashed lines in
the lower half indicate these are the same (e.g., Detect and Class) for both.
Figure 21. Operational States for PD
The PD input, typically an RJ-45 eight-lead connector, is referred to as the power interface (PI). PD input
requirements differ from PSE output requirements to account for voltage drops and operating margin. The
standard allots the maximum loss to the cable regardless of the actual installation to simplify implementation.
IEEE 802.3-2008 was designed to run over infrastructure including ISO/IEC 11801 class C (CAT3 per
TIA/EIA-568) that may have had AWG 26 conductors. IEEE 802.3at type 2 cabling power loss allotments and
voltage drops have been adjusted for 12.5
power loops per ISO/IEC11801 class D (CAT5 or higher per
TIA/EIA-568, typically AWG #24 conductors). Table 2 shows key operational limits broken out for the two
revisions of the standard.
16
Copyright 2008–2009, Texas Instruments Incorporated
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PDF描述 |
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| TPS2376PWR | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| TPS2375DRG4 | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| TPS2375DG4 | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| TPS2377DRG4 | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS23754PWP | 制造商:Texas Instruments 功能描述:Power Supply IC |
| TPS23754PWP-1 | 功能描述:熱插拔功率分布 IEEE 802.3at PoE Int & Iso Cnvrtr Cntrlr 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 |
| TPS23754PWPR | 功能描述:熱插拔功率分布 Hi Pwr/Hi Eff PoE Inter & DC/DC Cntrlr 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 |
| TPS23754PWPR-1 | 功能描述:熱插拔功率分布 IEEE 802.3at PoE Int & Iso Cnvrtr Cntrlr 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 |
| TPS23756EVM | 功能描述:電源管理IC開(kāi)發(fā)工具 TPS23756 Eval Mod RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類(lèi)型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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