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| 型号： | LM2575T-ADJG |
| 厂商： | ON Semiconductor |
| 文件页数： | 21/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1A TO220-5 |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.23 V ~ 37 V |
| 输入电压： | 4.75 V ~ 40 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： | TO-220-5 |
| 包装： | 管件 |
| 供应商设备封装： | TO-220-5 |
| 产品目录页面： | 1116 (CN2011-ZH PDF) |
| 其它名称： | LM2575T-ADJGOS |
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LM2575, NCV2575
If the input voltage is greater than ? 12 V, the output will rise
above ? 12 V accordingly, but will not damage the regulator.
cause some problems by coupling the ripple into the
ON/OFF pin, the regulator could be switched periodically
on and off with the line (or double) frequency.
+V in
LM2575 ? 12
4
Feedback
C out
1000 m F
/16 V
+V in
+V in
1
LM2575 ? XX
C in
100 m F
/50 V
1
3
GND
5
Output
2
ON/OFF
D1
1N5817
Regulated
Output
V out = -12 V
C in
100 m F
C1
0.1 m F
R1
5
ON/OFF 3
GND
R2
Unregulated
DC Input
L1
150 m H
Load Current from
200 mA for V in = -5.2 V
to 500 mA for V in = -7.0 V
47 k
47 k
NOTE: This picture does not show the complete circuit.
V [ V ) 1 ) R2 V (Q1)
-V in = -5.0 V to -12 V
Figure 29. Negative Boost Regulator
Design Recommendations:
The same design rules as for the previous inverting
buck ? boost converter can be applied. The output capacitor
C out must be chosen larger than would be required for a
standard buck converter. Low input voltages or high output
currents require a large value output capacitor (in the range
of thousands of m F). The recommended range of inductor
values for the negative boost regulator is the same as for
inverting converter design.
Another important point is that these negative boost
converters cannot provide current limiting load protection in
the event of a short in the output so some other means, such
as a fuse, may be necessary to provide the load protection.
Figure 30. Delayed Startup Circuitry
Undervoltage Lockout
Some applications require the regulator to remain off until
the input voltage reaches a certain threshold level. Figure 31
shows an undervoltage lockout circuit applied to a buck
regulator. A version of this circuit for buck ? boost converter
is shown in Figure 32. Resistor R3 pulls the ON/OFF pin
high and keeps the regulator off until the input voltage
reaches a predetermined threshold level, which is
determined by the following expression:
th Z1 R1 BE
Delayed Startup
There are some applications, like the inverting regulator
+V in
+V in
1
LM2575 ? 5.0
already mentioned above, which require a higher amount of
startup current. In such cases, if the input power source is
R2
10 k
R3
47 k
C in
100 m F 5
ON/OFF 3
GND
limited, this delayed startup feature becomes very useful.
To provide a time delay between the time the input voltage
is applied and the time when the output voltage comes up,
Z1
1N5242B
the circuit in Figure 30 can be used. As the input voltage is
applied, the capacitor C1 charges up, and the voltage across
the resistor R2 falls down. When the voltage on the ON/OFF
pin falls below the threshold value 1.4 V, the regulator starts
R1
10 k
Q1
2N3904
V th ≈ 13 V
up. Resistor R1 is included to limit the maximum voltage
applied to the ON/OFF pin, reduces the power supply noise
sensitivity, and also limits the capacitor C1 discharge
current, but its use is not mandatory.
When a high 50 Hz or 60 Hz (100 Hz or 120 Hz
respectively) ripple voltage exists, a long delay time can
NOTE: This picture does not show the complete circuit.
Figure 31. Undervoltage Lockout Circuit for
Buck Converter
http://onsemi.com
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2575T-ADJG | 制造商:ON Semiconductor 功能描述:IC STEP-DOWN REGULATOR TO-220-5 制造商:ON Semiconductor 功能描述:IC, STEP-DOWN REGULATOR, TO-220-5 |
| LM2575T-ADJ-H | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Voltage-Mode SMPS Controller |
| LM2575TADJLF02 | 制造商:National Semiconductor 功能描述:Conv DC-DC Single Step Down 4V to 40V 5-Pin(5+Tab) TO-220 Rail |
| LM2575T-ADJ-V | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Voltage-Mode SMPS Controller |
| LM2575TV | 制造商:HTC 制造商全称:HTC Korea TAEJIN Technology Co. 功能描述:1A, 52kHz, Step-Down Switching Regulator |
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