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參數(shù)資料
| 型號(hào)： | TPS2371D |
| 廠商： | Texas Instruments |
| 文件頁數(shù)： | 2/19頁 |
| 文件大小： | 0K |
| 描述： | IC PWR INTRFCE SW FOR POE 8-SOIC |
| 標(biāo)準(zhǔn)包裝： | 75 |
| 應(yīng)用： | 用于以太網(wǎng)供電（PoE）設(shè)備的電源接口開關(guān) |
| 接口： | IEEE 802.3af |
| 封裝/外殼： | 8-SOIC（0.154"，3.90mm 寬） |
| 供應(yīng)商設(shè)備封裝： | 8-SOIC |
| 包裝： | 管件 |
| 安裝類型： | 表面貼裝 |
| 產(chǎn)品目錄頁面： | 1013 (CN2011-ZH PDF) |
| 其它名稱： | 296-15960-5 |
TPS2371
SLUS566A JULY 2003 REVISED NOVEMBER 2003
10
www.ti.com
APPLICATION INFORMATION
Using EN_DC as a SoftStart or a PowerGood Function
The EN_DC pin is an output intended for use as a soft-start for a dc-to-dc converter. During the initial turn-on
of the pass FET, an internal 80-
A current sink is enabled on the EN_DC pin. This internal current sink is
removed only after the load capacitance has been charged to within 1.5-V of the supply voltage. By connecting
the EN_DC output to the soft start capacitor of a dc-to-dc converter, the internal current sink keeps the dc-to-dc
converter off during startup. Once the voltage across the converter has reached within 1.5 V of full voltage, the
dc-to-dc converter is allowed to soft start. A 5-V zener diode connected between EN_DC and RTN is required
for operation in this architecture.
For operation as a powergood output, the EN_DC requires an external pull-up.
A 1-M
resistor is
recommended. The EN_DC output also requires a clamp to limit the output voltage to within recommended
operating levels. A 5-V zener diode connected between EN_DC and RTN (pin 5 of the TPS2371) is
recommended. This configuration allows the EN_DC pin to act as an open drain output with which many
designers are more familiar.
SURGE SUPPRESSION
As specified in the Absolute Maximum Ratings table, the absolute maximum input voltage of the TPS2371 is
68 V. The IEEE 802.3af Power-Over-Ethernet Standard specifies the voltage range of PSE output is between
44 V asd 57 V. This PSE output voltage range would be reduced by cable, connector and other IR drops
between the PSE and the TPS2371 in the PD. However, the use of extended cable lengths and transformers
in some applications may induce transients in excess of 68 V during a hot plug event. To manage these transient
events and keep them from significantly exceeding the application’s maximum voltage, a transorb such as the
SMAJ54A should be placed between the positive input supply, VDD (pin 8), and the negative input supply, VEE
(pin 4). This, combined with a 0.1-
F bypass capacitor in parallel with the transorb helps to protect the TPS2371
from damage caused by transients during hot plug events. The transorb or zener diode should be selected such
that it does not zener below the maximum required application voltage of 57 V, but before reaching the 68-V
absolute maximum rating. For layout purposes, the 0.1-
F capacitor should be placed as close as possible to
the device; the transorb or zener diode should be placed as close to the supply connector as possible. Based
on the nature of the PD application, these measures should be considered an implementation requirement.
USE OF BARREL RECTIFIERS
Many applications use barrel rectifiers after the RJ-45 connector in order to be polarity insensitive. Barrel
rectifiers in front of the TPS2371 cause the voltages at the device to be lower than the voltages at the RJ-45.
The TPS2371 allows for this and is IEEE802.3af compliant during the detection and classification phases. For
the detection phase, the device begins detection for voltages as low as 1.3 V across the supply pins. For the
optional classification phase, the device is guaranteed to start classification below 14 V across the supply pins.
Once classification has been engaged, it becomes latched-in and further voltage drops due to cable resistance
and class current does not cause it to switch out of classification. However, in cases where the PSE is operating
at minimum class voltage (15.5 V) and there is a 20-
, 100-m cable between the PSE and the PD, Class 3
devices may not classify correctly when using barrel rectifiers. Class 3 device designs should include schottky
diodes to handle all corner cases or switch to Class 0 devices when using barrel rectifiers.
Thermal Shutdown
In the event of a short circuit or overload condition, the TPS2371 begins to heat up until thermal shutdown is
reached. Once thermal shutdown is reached, the internal FET is switched off, removing the load from the supply.
After the device has cooled sufficiently, it retries by restarting the internal FET. If the overload or short is not
removed, the device cycles thermal shutdown seven times before latching the internal FET off. Once the internal
FET is latched off, power needs to be cycled to reset the latch.
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| TPS2371DG4 | 功能描述:熱插拔功率分布 Legacy/IEEE802.3af Comp Pwr InterfSw 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 |
| TPS2371DR | 功能描述:熱插拔功率分布 Legacy/IEEE802.3af Comp Pwr InterfSw 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 |
| TPS2371DRG4 | 功能描述:熱插拔功率分布 Legacy/IEEE802.3af Comp Pwr InterfSw 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 |
| TPS2371PW | 功能描述:熱插拔功率分布 Legacy/IEEE802.3af Comp Pwr InterfSw 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 |
| TPS2371PWG4 | 功能描述:熱插拔功率分布 Legacy/IEEE802.3af Comp Pwr InterfSw 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 |
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