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| 型号： | TPS2375PWR-1 |
| 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, TSSOP-8 |
| 文件页数： | 8/25页 |
| 文件大小： | 623K |
| 代理商： | TPS2375PWR-1 |
ESD
EXTERNAL COMPONENTS
Transformer
Input Diodes or Diode Bridges
Input Capacitor
Load Capacitor
C v
I
(PD)
180
10 mA
(2)
data sheet
SLVS570A – MARCH 2005 – REVISED APRIL 2008 ......................................................................................................................................................... www.ti.com
The TPS2375-1 has been tested using the surge of EN61000-4-2 in an evaluation module (EVM) using the
circuit in Figure 1. The levels used were 8-kV contact discharge and 15-kV air discharge. Surges were applied
between the RJ-45 and the dc EVM outputs, and between an auxiliary power input jack and the dc outputs. No
failures were observed.
ESD requirements for a unit that incorporates the TPS2375-1 have much broader scope and operational
implications than those used in TI’s testing. Unit level requirements should not be confused with EVM testing that
only validated the TPS2375-1.
Nodes on an Ethernet network commonly interface to the outside world via an isolation transformer per IEEE
802.3 requirements (see Figure 1). For powered devices, the isolation transformer must include a center tap on
the media (cable) side. Proper termination is required around the transformer to provide correct impedance
matching and to avoid radiated and conducted emissions. Transformers must be specifically rated to work with
the Ethernet chipset, and the IEEE 802.3af standard.
The IEEE 802.3af requires the PD to accept power on either set of input pairs in either polarity. This requirement
is satisfied by using two full-wave input bridge rectifiers as shown in Figure 1. Silicon p-n diodes with a 1-A or
1.5-A rating and a minimum breakdown of 100 V are recommended. Diodes exhibit large dynamic resistance
under low-current operating conditions such as in detection. The diodes should be tested for their behavior under
this condition. The diode forward drops must be less than 1.5 V at 500
A and at the lowest operating
temperature.
The IEEE 802.3af requires a PD input capacitance between 0.05
F and 0.12 F during detection. This capacitor
should be located directly adjacent to the TPS2375-1 as shown in Figure 1. A 100-V, 10%, X7R ceramic
capacitor meets the specification over a wide temperature range.
The IEEE 802.3af specification requires that the PD maintain a minimum load capacitance of 5
F. It is
permissible to have a much larger load capacitor, and the TPS2375-1 can charge in excess of 470
F before
thermal issues become a problem. However, if the load capacitor is too large, the PD design may violate IEEE
802.3af requirements.
If the load capacitor is too large, there can be a problem with inadvertent power shutdown by the PSE caused by
failure to meet the MPS. This is caused by having a long input current dropout due to a drop in input voltage with
a large capacitance-to-load ratio. The standard gives Equation 2:
where C is the bulk capacitance in
F and I
(PD) is the PD load current in mA.
A particular design may have a tendency to cause ringing at the RTN pin during startup, inadvertent hot-plugs of
the PoE input, or plugging in a wall adapter. It is recommended that a minimum value of 1
F be used at the
output of the TPS2375-1 if downstream filtering prevents placing the larger bulk capacitor right on the output.
When using ORing option 2, it is recommended that a large capacitor such as a 22
F be placed across the
TPS2375-1 output.
16
Copyright 2005–2008, Texas Instruments Incorporated
Product Folder Link(s): TPS2375-1 TPS2377-1
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS2375PWR-1G4 | 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 |
| TPS2375PWRG4 | 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 |
| TPS2376D | 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 |
| TPS2376DDA-H | 功能描述:热插拔功率分布 IEEE 802.3af PoE High Power PD Cont 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 |
| TPS2376DDA-HG4 | 功能描述:热插拔功率分布 IEEE 802.3af PoE High Power PD Cont 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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