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參數(shù)資料
| 型號： | LM2585S-12 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SIMPLE SWITCHER 3A Flyback Regulator |
| 中文描述： | 7 A SWITCHING REGULATOR, 125 kHz SWITCHING FREQ-MAX, PSSO5 |
| 封裝： | TO-263, 5 PIN |
| 文件頁數(shù)： | 20/25頁 |
| 文件大?。?/td> | 627K |
| 代理商： | LM2585S-12 |
Application Hints
PROGRAMMING OUTPUT VOLTAGE
(SELECTING R
1
AND R
2
)
Referring to the adjustable regulator in Figure 38 the output
voltage is programmed by the resistors R
1
and R
2
by the fol-
lowing formula:
V
OUT
= V
REF
(1 + R
1
/R
2
)
Resistors R
and R
divide the output voltage down so that
it can be compared with the 1.23V internal reference. With
R
2
between 1k and 5k, R
1
is:
R
1
= R
2
(V
OUT
/V
REF
1)
For best temperature coefficient and stability with time, use
1% metal film resistors.
where V
REF
= 1.23V
where V
REF
= 1.23V
SHORT CIRCUIT CONDITION
Due to the inherent nature of boost regulators, when the out-
put is shorted (see Figure 38), current flows directly from the
input, through the inductor and the diode, to the output, by-
passing the switch. The current limit of the switch does not
limit the output current for the entire circuit. To protect the
load and prevent damage to the switch, the current must be
externally limited, either by the input supply or at the output
with an external current limit circuit. The external limit should
be set to the maximum switch current of the device, which is
3A.
In a flyback regulator application (Figure 39), using the stan-
dard transformers, the LM2585 will survive a short circuit to
the main output. When the output voltage drops to 80% of its
nominal value, the frequency will drop to 25 kHz. With a
lower frequency, off times are larger. With the longer off
times, the transformer can release all of its stored energy be-
fore the switch turns back on. Hence, the switch turns on ini-
tially with zero current at its collector. In this condition, the
switch current limit will limit the peak current, saving the
device.
DS012515-55
FIGURE 38. Boost Regulator
DS012515-56
FIGURE 39. Flyback Regulator
www.national.com
20
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2585S-12/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2585S-3.3 | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2585S-3.3/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2585S-5.0 | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2585S-5.0/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
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