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參數(shù)資料
| 型號(hào)： | LM2574N-15/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | DIP-8 |
| 文件頁數(shù)： | 13/33頁 |
| 文件大?。?/td> | 814K |
| 代理商： | LM2574N-15/NOPB |
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Additional Applications (Continued)
Because of the boosting function of this type of regulator, the
switch current is relatively high, especially at low input volt-
ages. Output load current limitations are a result of the maxi-
mum current rating of the switch. Also, boost regulators can
not provide current limiting load protection in the event of a
shorted load, so some other means (such as a fuse) may be
necessary.
UNDERVOLTAGE LOCKOUT
In some applications it is desirable to keep the regulator off
until the input voltage reaches a certain threshold. An under-
voltage lockout circuit which accomplishes this task is shown
in
Figure 13 while Figure 14 shows the same circuit applied
to a buck-boost configuration. These circuits keep the regu-
lator off until the input voltage reaches a predetermined
level.
V
TH ≈ VZ1 +2VBE (Q1)
DELAYED STARTUP
The ON /OFF pin can be used to provide a delayed startup
feature as shown in
Figure 15. With an input voltage of 20V
and for the part values shown, the circuit provides approxi-
mately 10 ms of delay time before the circuit begins switch-
ing. Increasing the RC time constant can provide longer de-
lay times. But excessively large RC time constants can
cause problems with input voltages that are high in 60 Hz or
120 Hz ripple, by coupling the ripple into the ON /OFF pin.
ADJUSTABLE OUTPUT, LOW-RIPPLE POWER SUPPLY
A 500 mA power supply that features an adjustable output
voltage is shown in
Figure 16. An additional L-C filter that re-
duces the output ripple by a factor of 10 or more is included
in this circuit.
DS011394-20
Note: Pin numbers are for 8-pin DIP package.
FIGURE 12. Negative Boost
DS011394-21
Note: Complete circuit not shown.
Note: Pin numbers are for 8-pin DIP package.
FIGURE 13. Undervoltage Lockout for Buck Circuit
DS011394-22
Note: Complete circuit not shown (see
Figure 11 ).
Note: Pin numbers are for 8-pin DIP package.
FIGURE 14. Undervoltage Lockout
for Buck-Boost Circuit
DS011394-23
Note: Complete circuit not shown.
Note: Pin numbers are for 8-pin DIP package.
FIGURE 15. Delayed Startup
www.national.com
20
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2574M-15/NOPB | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PDSO14 |
| LM2574-ADJMDC | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, UUC |
| LM2574-12MDC | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, UUC |
| LM2574-5.0MDC | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, UUC |
| LM2574-3.3MDC | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, UUC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2574N-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 |
| LM2574N-3.3 NOPB | 制造商:National Semiconductor 功能描述:Conv DC-DC Single Step Down 4V to 40V 8-Pin PDIP Rail |
| LM2574N-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 |
| LM2574N-3.3G | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3.3V 500mA Buck PWM RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM2574N33 | 制造商:Texas Instruments 功能描述:SWITCHING REG 0.5A 3.3V 2574 DIP8 |
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