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参数资料
| 型号： | LM2574-15MWC |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, UUC |
| 封装： | WAFER |
| 文件页数： | 13/33页 |
| 文件大小： | 814K |
| 代理商： | LM2574-15MWC |
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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
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2574-3.3 | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:EASY SWITCHERE⑩ 0.5 A STEP-DOWN VOLTAGE REGULATOR |
| LM2574-3.3BN | 功能描述:IC REG BUCK 3.3V 0.5A 8DIP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:20 系列:SIMPLE SWITCHER® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:12V 输入电压:4 V ~ 60 V PWM 型:电压模式 频率 - 开关:52kHz 电流 - 输出:1A 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:通孔 封装/外壳:16-DIP（0.300"，7.62mm） 包装:管件 供应商设备封装:16-DIP 其它名称:*LM2575HVN-12LM2575HVN-12 |
| LM2574-3.3BWM | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LM2574-3.3HVN | 制造商:NSC 制造商全称:National Semiconductor 功能描述:SIMPLE SWITCHER⑩ 0.5A Step-Down Voltage Regulator |
| LM2574-3.3YN | 功能描述:直流/直流开关调节器 0.5A Step-Down SMPS Regulator (Lead Free) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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