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參數(shù)資料
| 型號： | TPS2398DGKRG4 |
| 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, MSOP-8 |
| 文件頁數(shù)： | 7/27頁 |
| 文件大?。?/td> | 792K |
| 代理商： | TPS2398DGKRG4 |
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TPS2398
TPS2399
SLUS562A JUNE 2003 REVISED SEPTEMBER 2003
15
www.ti.com
APPLICATION INFORMATION
setting the sense resistor value
Due to the current-limiting action of the internal LCA, the maximum allowable load current for an implementation
is easily programmed by selecting the appropriate sense resistor value. The LCA acts to limit the sense voltage
VI(ISENS) to its internal reference. Once the voltage at the IRAMP pin exceeds approximately 4 V, this limit is
the clamp voltage, VREF_K. Therefore, a maximum sense resistor value can be determined from equation (1).
R
SENSE v
33 mV
IMAX
where:
R
SENSE is the resistor value, and
IMAX is the desired current limit.
When setting the sense resistor value, it is important to consider two factors, the minimum current that may be
imposed by the TPS2398 or TPS2399, and the maximum load under normal operation of the module. For the
first factor, the specification minimum clamp value is used, as seen in equation (1). This method accounts for
the tolerance in the sourced current limit below the typical level expected (40 mV/RSENSE). (The clamp
measurement includes LCA input offset voltage; therefore, this offset does not have to be factored into the
current limit again.) Second, if the load current varies over a range of values under normal operating conditions,
then the maximum load level must be allowed for by the value of RSENSE. One example of this is when the load
is a switching converter, or brick, which draws higher input current, for a given power output, when the
distribution bus is at the low end of its operating range, with decreasing draw at higher supply voltages. To avoid
current-limit operation under normal loading, some margin should be designed in between this maximum
anticipated load and the minimum current limit level, or IMAX > ILOAD(max), for equation (1).
For example, using a 20-m
sense resistor for a nominal 1-A load application provides a minimum of 650 mA
of overhead for load variance/margin. Typical bulk capacitor charging current during turn-on is 2 A
(40 mV/20 m
).
setting the inrush slew rate
The TPS2398 and TPS2399 devices enable user-programming of the maximum current slew rate during load
start-up events. A capacitor tied to the IRAMP pin (C2 in the typical application diagram) controls the di/dt rate.
Once the sense resistor value has been established, a value for ramp capacitor CIRAMP, in microfarads, can be
determined from equation (2).
C
IRAMP +
11
100
R
SENSE
di
dt MAX
where:
R
SENSE is in ohms, and
(di/dt)
MAX is the desired maximum slew rate, in amperes/second.
For example, if the desired slew rate for the typical application shown is 1500 mA/ms, the calculated value for
CIRAMP is about 3700 pF. Selecting the next larger standard value of 3900 pF (as shown in the diagram) provides
some margin for capacitor and sense resistor tolerances.
(1)
(2)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS2398EVM | 功能描述:電源管理IC開發(fā)工具 TPS2398 Eval Mod RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| TPS2399D | 制造商:Texas Instruments 功能描述: |
| TPS2399DGK | 功能描述:熱插拔功率分布 Simple -48V Controller w/Enable 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: 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| TPS2399DGKG4 | 功能描述:熱插拔功率分布 Simple -48V Controller w/Enable 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: 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| TPS2399DGKR | 功能描述:熱插拔功率分布 Simple -48V Controller w/Enable 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: 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
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