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參數資料
| 型號： | TPS2421-2DDAR |
| 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： | PLATSIC, SOP-8 |
| 文件頁數： | 5/24頁 |
| 文件大小： | 1297K |
| 代理商： | TPS2421-2DDAR |
2
IN
MIN
V
R
12
=
(
)
NOM
LOAD
SPIKE absolute
L
V
I
C
=
+
( )
straightwire
4 L
L
0.2 L ln
0.75
nH
D
-
÷
è
www.ti.com
SLUS907D – JANUARY 2009 – REVISED AUGUST 2010
APPLICATION INFORMATION
Maximum Load at Startup
The power limiting function of the TPS2421 provides very effective protection for the internal FET. Expectedly,
there is a supply voltage dependent maximum load which the device will be able to power up. Loads above this
level may cause the device to shut off current before startup is complete. Neglecting any load capacitance, the
maximum load ( minimum load resistance ) is calculated using the equation;
(5)
Adding load capacitance may reduce the maximum load which can be present at start up.
If EN is tied to GND at startup and VIN does not ramp quickly the TPS2421 may momentarily turn off then on
during startup. This can happen if a capacitive load momentarily pulls down the input voltage below the UV
threshold. If necessary, this can be avoided by delaying EN assertion until VIN is fully up.
Transient Protection
The need for transient protection in conjunction with hot-swap controllers should always be considered. When
the TPS2421 interrupts current flow, input inductance generates a positive voltage spike on the input and output
inductance generates a negative voltage spike on the output. Such transients can easily exceed twice the supply
voltage if steps are not taken to address the issue. Typical methods for addressing transients include;
Minimizing lead length/inductance into and out of the device
Voltage Suppressors (TVS) on the input to absorb inductive spikes
Shottky diode across the output to absorb negative spikes
A combination of ceramic and electrolytic capacitors on the input and output to absorb energy
Use PCB GND planes
The following equation estimates the magnitude of these voltage spikes:
where
VNOM is the nominal supply voltage
ILOAD is the load current
C is the capacitance present at the input or output of the TPS2421
L equals the effective inductance seen looking into the source or the load
(6)
Calculating the inductance due to a straight length of wire is shown in Equation 7.
where
L is the length of the wire
D is diameter of the wire
(7)
Some applications may require the addition of a TVS to prevent transients from exceeding the absolute ratings if
sufficient capacitance cannot be included.
Copyright 2009–2010, Texas Instruments Incorporated
13
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| TPS2421-2EVM-03 | 功能描述:電源管理IC開發工具 TPS2421-2 Hot Swap Controller Eval Mod RoHS:否 制造商:Maxim Integrated 產品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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| TPS2456EVM | 功能描述:電源管理IC開發工具 TPS2456 Eval Mod RoHS:否 制造商:Maxim Integrated 產品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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