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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)： | 23/23頁 |
| 文件大?。?/td> | 640K |
| 代理商： | TPS2376DDAR-H |
www.ti.com
APPLICATION INFORMATION
OVERVIEW
Normal Operation
57
42
36
30
20.5
14.5
10.1
2.7
Detection
Lower
Limit
Detection
Upper
Limit
Classification
Lower
Limit
Classification
Upper
Limit
Must
T
urn
Off
by
V
oltage
Falling
Lower
Limit
Proper
Operation
Must
T
urn
On
by
V
oltage
Rising
Maximum
Input
V
oltage
Detect
Classify
Shut -
down
PI Voltage (V)
0
SLVS646A – SEPTEMBER 2006 – REVISED SEPTEMBER 2006
The IEEE 802.3af specification defines a process for safely providing power over an ethernet cable when a
capable device is connected, and then removing power if it is disconnected. The process proceeds through
three operational states: detection, classification, and operation. An unterminated cable is not powered. The
PSE periodically probes the cable with low voltage, looking for a 25 k
signature; this is referred to as detection.
The low power levels used during detection are unlikely to cause damage to devices not designed for PoE. If a
valid powered device (PD) signature is present during detection, then the PSE may optionally inquire about the
amount of power the PD requires; this is referred to as classification. The PD may return a default full-power
signature, or one of four other defined choices. In a high-power system, class may not be required, or the levels
may be redefined to suit that particular system. The PSE may use the class power to determine if it has
adequate power to operate this device, and later to determine if a device is using more power than it requested.
At this point in the process, the PSE may choose to power the PD. The PSE output is protected against shorts
and overloads when the PD is powered. The maintain power signature (MPS) is presented by the powered PD
to assure the PSE that it is present. The MPS is either a minimum dc current, a maximum ac impedance, or
both. When the MPS disappears, the PSE removes power and returns to its initial state. Figure 12 shows the
operational states as a function of PD input voltage range as defined in IEEE 802.3af.
The PD input is typically an RJ-45 (8-pin) connector, referred to as the power interface (PI). PD input
requirements differ from PSE output requirements to account for voltage drops in the cable. The IEEE 802.3af
specification uses a cable resistance of 20
to derive the voltage limits at the PD from the PSE output
requirements. While the 20
specification covers telecom type wiring, CAT-5 infrastructure will meet a 12.5
limit. Specifying the high-power system to operate over CAT-5 cable allows significantly more power to be
delivered.
A high-power nonstandard system need not support all combinations of voltage delivery polarities and pair sets.
The IEEE 802.3af PSE allows voltage of either polarity between the RX and TX pairs, or between the two spare
pairs. An input diode or bridge is recommended to provide reverse input polarity protection. The bridge
maintains compatibility with auto-MDIX systems that have reverse RX-TX pair assignments. The voltage drops
associated with the input diode(s) cause a difference between the limits at the PI and the TPS2376-H
specifications.
Two-pair power delivery is the simplest to implement, and is preferred if adequate power can be achieved.
Application report SLVA225 presents a number of considerations for a high power PoE end-to-end system.
Power delivery on all four pairs is significantly more complex, and is only recommended when two pair systems
do not suffice. Considerations for high power systems are presented in Application Report SLVA225.
The following discussion is intended as an aid in understanding the operation of the TPS2376-H, but not as a
substitute for the IEEE 802.3af standard. Standards change and should always be referenced when making
design decisions.
Figure 12. IEEE 802.3 PD Voltage Limits
9
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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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