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參數(shù)資料
| 型號： | TPS23753PW |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.505 A SWITCHING CONTROLLER, 273 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | GREEN, PLASTIC, TSSOP-14 |
| 文件頁數(shù)： | 5/30頁 |
| 文件大?。?/td> | 823K |
| 代理商： | TPS23753PW |
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Normal Operation
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Detect
Classify
Shut-
down
PI Voltage (V)
0
3/06/08
www.ti.com
SLVS853C – JUNE 2008 – REVISED JANUARY 2010
APPLICATIONS
Classic PoE Overview
The following text is intended as an aid in understanding the operation of the TPS23753 but not as a substitute
for the actual 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 will be referred to as a Type 1 device, and devices with high power or 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, 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 may
inquire how much power the PD requires; this is referred to as classification. Type 2 PSEs are required to do
hardware classification. The PD may return the default 13W current-encoded class, or one of four other choices.
The PSE may then power the PD if it has adequate capacity. 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 16 shows the
operational states as a function of PD input voltage.
Figure 16. IEEE 802.3at (Type 1) Operational States
The PD input is typically an RJ-45 eight-lead connector which is referred to as the power interface (PI). PD input
requirements differ from PSE output requirements to account for voltage drops in the cable and operating
margin. The IEEE 802.3at standard uses a cable resistance of 20
(for type 1 devices) to derive the voltage
limits at the PD based on the PSE output voltage requirements. Although the standard specifies an output power
of 15.4 W at the PSE, only 13 W is available at the PI due to the worst-case power loss in the cable. The PSE
can apply voltage either between the RX and TX pairs (pins 1–2 and 3–6 for 10baseT or 100baseT), or between
the two spare pairs (4–5 and 7–8). The PSE may only apply voltage to one set of pairs at a time. The PD uses
input diode bridges to accept power from any of the possible PSE configurations. The voltage drops associated
with the input bridges create a difference between the standard limits at the PI and the TPS23753 specifications.
The PSE is permitted to disconnect a PD if it draws more than its maximum class power over a one second
interval. A type 1 PSE compliant to IEEE 802.3at is required to limit current to between 400 mA and an
upper-bound template (IEEE 802.3-2008 was 450 mA) during powered operation. The PSE must disconnect the
PD if it draws this current for more than 75 ms. Class 0 and 3 PDs may draw up to 400 mA peak currents for up
to 50 ms. The PSE may set lower output current limits based on the PD’s declared power requirements.
Threshold Voltages
The TPS23753 has a number of internal comparators with hysteresis for stable switching between the various
states as shown in Figure 16. Figure 17 relates the parameters in the Electrical Characteristics section to the
PoE states. The mode labeled idle between classification and operation implies that the DEN, CLS, and RTN
pins are all high impedance.
Copyright 2008–2010, Texas Instruments Incorporated
13
Product Folder Link(s): TPS23753
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS23753PW | 制造商:Texas Instruments 功能描述:Controller IC |
| TPS23753PWG4 | 功能描述:熱插拔功率分布 PoE Interface & 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 |
| TPS23753PWR | 功能描述:熱插拔功率分布 Interface and Iso Cnvrtr and 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 |
| TPS23753PWRG4 | 功能描述:熱插拔功率分布 PoE Interface & 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 |
| TPS23754EVM-383 | 功能描述:電源管理IC開發(fā)工具 TPS23754 Eval Mod 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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