- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄371379 > 2377 (Texas Instruments, Inc.) IEEE 802.3af PoE POWERED DEVICE CONTROLLERS WITH AUTO-RETRY PDF資料下載
參數(shù)資料
| 型號： | 2377 |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | IEEE 802.3af PoE POWERED DEVICE CONTROLLERS WITH AUTO-RETRY |
| 中文描述： | IEEE 802.3af標準的PoE用電設備控制器，自動重試 |
| 文件頁數(shù)： | 16/23頁 |
| 文件大?。?/td> | 649K |
| 代理商： | 2377 |
www.ti.com
ESD
EXTERNAL COMPONENTS
Transformer
Input Diodes or Diode Bridges
Input Capacitor
The IEEE 802.3af requires a PD input capacitance between 0.05 μF and 0.12
μ
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.
Load Capacitor
The IEEE 802.3af specification requires that the PD maintain a minimum load capacitance of 5
μ
F. It is
permissible to have a much larger load capacitor, and the TPS2375-1 can charge in excess of 470 μF before
thermal issues become a problem. However, if the load capacitor is too large, the PD design may violate IEEE
802.3af requirements.
C
I(PD)
180
10 mA
(2)
TPS2375-1
TPS2377-1
SLVS570–MARCH 2005
APPLICATION INFORMATION (continued)
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 μA and at the lowest operating
temperature.
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
μ
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 μF 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
μ
F be placed across the
TPS2375-1 output.
16
相關PDF資料 |
PDF描述 |
|---|---|
| 2377-1 | IEEE 802.3af PoE POWERED DEVICE CONTROLLERS WITH AUTO-RETRY |
| 238.2 | 5 Volt and 3.3 Volt MicroMonitor |
| 238.25 | Fuse |
| 238.3 | 5 Volt and 3.3 Volt MicroMonitor |
| 238.4 | Fuse |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| 23-770 | 制造商:MCM 功能描述:1M RA DC EXTENSION CORD 2.1MM DC PLUG; 2.1MM DC JACK |
| 23770-000-55 | 制造商:Konig & Meyer 功能描述:4 Piece Microphone Fish Pole |
| 2377-01 | 制造商:Bourns Inc 功能描述:GLASS TUBE PRODUCT |
| 2377-05-020 | 制造商:Coto Technology 功能描述:RELAY REED DPST 500MA 5V |
| 23-770I | 制造商:-- 功能描述:MODULAR ADAPTER, DB25-M TO RJ45 W/KEY, IVORY |
發(fā)布緊急采購，3分鐘左右您將得到回復。