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參數(shù)資料
| 型號： | TPS2376DDA-HG4 |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 電源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封裝： | GREEN, PLASTIC, POWER PAD, SOIC-8 |
| 文件頁數(shù)： | 3/23頁 |
| 文件大?。?/td> | 640K |
| 代理商： | TPS2376DDA-HG4 |
www.ti.com
PROGRAMMABLE INRUSH CURRENT LIMIT AND FIXED OPERATIONAL CURRENT LIMIT
THERMAL PROTECTION
MAINTAIN POWER SIGNATURE
POWER GOOD
SLVS646A – SEPTEMBER 2006 – REVISED SEPTEMBER 2006
APPLICATION INFORMATION (continued)
Inrush limiting has several benefits. First, it maintains the cable voltage above the UVLO turn-off threshold as
the bulk capacitor charges. Second, it keeps the PSE from going into current limit. This reduces stress on the
PSE and allows an arbitrarily large bulk capacitor to be charged. Third, the inrush limit is used as the foldback
current during a hard overload.
The TPS2376-H operational current limit protects the internal power switch from sudden output faults and
current surges. The minimum operational current limit level of 625 mA lies above the minimum TPS23841 output
current limit of 600 mA. This current limit enables the PD to draw the maximum available power.
The TPS2376-H incorporates a state machine that controls the inrush and operational current limit states. When
V(VDD) is below the lower UVLO threshold, the current limit state machine is reset. In this condition, the RTN pin
is high impedance, and floats to V(VDD) once the output capacitor is discharged. When V(VDD) rises above the
UVLO turn on threshold, the TPS2376-H enables the internal power MOSFET with the current limit set to the
inrush value programmed by R(ILIM). The load capacitor charges and the RTN pin voltage falls from V(VDD) to
nearly V(VSS). Once the inrush current falls about 10% below the programmed limit for 150-s, the current limit
switches to the 765-mA operational level and PG goes open-drain. The internal power MOSFET is disabled if
the input voltage drops below the lower UVLO threshold and the state machine is reset.
An output overload, or increasing input voltage step, may cause the operational current limit to become active.
The MOSFET voltage will then start to rise, causing high power dissipation. Current-limit foldback controls this
MOSFET power dissipation to a manageable level. Foldback is achieved by switching the current limit state
machine from the operational level to inrush when the MOSFET voltage exceeds 10 V for 150-
s. An additional
layer of protection is provided by thermal shutdown if the overload persists long enough.
Practical values of R(ILIM) lie between 125 k and 1 M; however, selecting lower inrush current values reduces
peak stresses under output-short circuit conditions. An inrush level of 140 mA, set by an R(ILIM) of 287 k, is
recommended for most applications.
The TPS2376-H may overheat if the ambient temperature becomes excessive, or if it operates for an extended
period of time in classification or current limit. The TPS2376-H protects itself by disabling the RTN and CLASS
pins and pulling PG low when the internal die temperature reaches about 140
°C. It automatically restarts when
the die temperature has fallen approximately 20
°C. If V
(RTN-VSS) is less than 10 V when the TPS2376-H restarts,
the current limit remains at 765 mA and PG goes open-drain. If the overload has caused V(RTN-VSS) to exceed 10
V while disabled, the current limit is set to the inrush level and PG remains low. This process is referred to as
thermal cycling. Thermal protection is active whenever the TPS2376-H is not in detection.
Short periods of thermal cycling do not significantly impact the reliability or life expectancy, but prolonged
periods may. Other components in the power path can be overstressed if this condition exists for a prolonged
time as well.
Once a valid PD has been detected and powered, the PSE uses the maintain power signature (MPS) to
determine when to remove power from the PI. The PSE removes power from that output port if it detects loss of
MPS for 300 ms or more. A valid MPS requires that the PD to draw at least 10 mA and have an ac impedance
less than 26.25 k
in parallel with 0.05 F.
The TPS2376-H includes a power-good (PG) output for use as a dc/dc converter enable once the load capacitor
is fully charged. The PG pin is the safest way to ensure that there are no undesired interactions between the
inrush limit, the converter startup characteristic, and the size of the bulk capacitor.
The PG output is pulled to RTN whenever the MOSFET is disabled, is in inrush current limiting, or the V(RTN)
rises above 10 V. The PG pin goes to an open-drain state approximately 150
s after the inrush current falls
10% below the regulated value. PG pull down current is only specified for V(VDD-RTN) greater than 4 V, below
which the dc/dc converter should not be able to operate. The PG interface to the downstream dc/dc converter is
simplified by referencing it to RTN.
11
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS2376DDAR-H | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Hi Pwr PD CONTROLLER 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 |
| TPS2376DDAR-HG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Hi Pwr PD CONTROLLER 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 |
| TPS2376DG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler 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 |
| TPS2376DR | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler 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 |
| TPS2376DRG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler 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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