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参数资料
| 型号： | TPS2375DG4 |
| 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, MS-012AA, SOIC-8 |
| 文件页数： | 2/24页 |
| 文件大小： | 579K |
| 代理商： | TPS2375DG4 |
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
INTERNAL THRESHOLDS
data sheet
SLVS525B – APRIL 2004 – REVISED APRIL 2008............................................................................................................................................................ www.ti.com
The IEEE 802.3af specification defines a process for safely powering a PD over a cable, and then removing
power if a PD is disconnected. The process proceeds through three operational states: detection, classification,
and operation. The intent behind the process is to leave an unterminated cable unpowered while the PSE
periodically checks for a plugged-in device; 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 PD signature is present, then
the PSE may optionally inquire how much power the PD requires; this is referred to as classification. The PD
may return a default full-power signature, or one of four other choices. Knowing the power demand of each PD
allows the PSE to intelligently allocate power between PDs, and also to protect itself against overload. The PSE
powers up a valid PD, and then monitors its output for overloads. The maintain power signature (MPS) is
presented by the powered PD to assure the PSE that it is there. The PSE monitors its output for the MPS to see
if the PD is removed, and turns the port off, if it loses the MPS. Loss of MPS returns the PSE to the initial state of
detection. Figure 18 shows the operational states as a function of PD input voltage range.
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 and margin. The
specification uses a cable resistance of 20
to derive the voltage limits at the PD from the PSE output
requirements. Although the standard specifies an output power of 15.4 W at the PSE output, there is only
12.95 W available at the input of the PD due to the worst case power loss in the cable.
The PSE can apply voltage either between the RX and TX pairs, or between the two spare pairs as shown in
Figure 1. The applied voltage can be of either polarity. The PSE cannot apply voltage to both paths at the same
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 cause a difference between the IEEE 802.3af limits at the PI and the
TPS2375 specifications.
The PSE is required to current limit between 350 mA and 400 mA during normal operation, and it must
disconnect the PD if it draws this current for more than 75 ms. The PSE may set lower output current limits
based on the PD advertised power requirements, as discussed below.
The following discussion is intended as an aid in understanding the operation of the TPS2375, but not as a
substitute for the actual IEEE 802.3af standard. Standards change and should always be referenced when
making design decisions.
Figure 18. IEEE 802.3 PD Limits
In order to implement the PoE functionality as shown in Figure 18, the TPS2375 has a number of internal
comparators with hysteresis for stable switching between the various states. Figure 19 relates the parameters in
the Electrical Characteristics section to the PoE states. The mode labeled idle between classification and
detection implies that the DET, CLASS, PG, and RTN pins are all high impedance.
10
Copyright 2004–2008, Texas Instruments Incorporated
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS2375DR | 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 |
| TPS2375DRG4 | 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 |
| TPS2375EVM | 功能描述:电源管理IC开发工具 TPS2375 POE Powed Device Eval Mod RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| TPS2375PW | 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 |
| TPS2375PW-1 | 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 |
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