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参数资料
| 型号： | LM2576T-12G |
| 厂商： | ON SEMICONDUCTOR |
| 元件分类： | 稳压器 |
| 英文描述： | 7.5 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PSFM5 |
| 封装： | LEAD FREE, TO-220, 5 PIN |
| 文件页数： | 7/28页 |
| 文件大小： | 275K |
| 代理商： | LM2576T-12G |
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LM2576
http://onsemi.com
15
Table 3. Example of Several Inductor Manufacturers Phone/Fax Numbers
Pulse Engineering, Inc.
Phone
Fax
+ 16196748100
+ 16196748262
Pulse Engineering, Inc. Europe
Phone
Fax
+ 3539324107
+ 3539324459
Renco Electronics, Inc.
Phone
Fax
+ 15166455828
+ 15165865562
Tech 39
Phone
Fax
+ 33141151681
+ 33147095051
Schott Corporation
Phone
Fax
+ 16124751173
+ 16124751786
EXTERNAL COMPONENTS
Input Capacitor (Cin)
The Input Capacitor Should Have a Low ESR
For stable operation of the switch mode converter a low
ESR (Equivalent Series Resistance) aluminium or solid
tantalum bypass capacitor is needed between the input pin
and the ground pin, to prevent large voltage transients from
appearing at the input. It must be located near the regulator
and use short leads. With most electrolytic capacitors, the
capacitance value decreases and the ESR increases with
lower temperatures. For reliable operation in temperatures
below 25
°C larger values of the input capacitor may be
needed. Also paralleling a ceramic or solid tantalum
capacitor will increase the regulator stability at cold
temperatures.
RMS Current Rating of Cin
The important parameter of the input capacitor is the RMS
current rating. Capacitors that are physically large and have
large surface area will typically have higher RMS current
ratings. For a given capacitor value, a higher voltage
electrolytic capacitor will be physically larger than a lower
voltage capacitor, and thus be able to dissipate more heat to
the surrounding air, and therefore will have a higher RMS
current rating. The consequence of operating an electrolytic
capacitor beyond the RMS current rating is a shortened
operating life. In order to assure maximum capacitor
operating lifetime, the capacitor’s RMS ripple current rating
should be:
Irms > 1.2 x d x ILoad
where d is the duty cycle, for a buck regulator
d
+
ton
T
+
Vout
V
in
and d
+
ton
T
+
|Vout|
|Vout| ) Vin
for a buck
*boost regulator.
Output Capacitor (Cout)
For low output ripple voltage and good stability, low ESR
output capacitors are recommended. An output capacitor
has two main functions: it filters the output and provides
regulator loop stability. The ESR of the output capacitor and
the peaktopeak value of the inductor ripple current are the
main factors contributing to the output ripple voltage value.
Standard aluminium electrolytics could be adequate for
some applications but for quality design, low ESR types are
recommended.
An aluminium electrolytic capacitor’s ESR value is
related to many factors such as the capacitance value, the
voltage rating, the physical size and the type of construction.
In most cases, the higher voltage electrolytic capacitors have
lower ESR value. Often capacitors with much higher
voltage ratings may be needed to provide low ESR values
that, are required for low output ripple voltage.
The Output Capacitor Requires an ESR Value
That Has an Upper and Lower Limit
As mentioned above, a low ESR value is needed for low
output ripple voltage, typically 1% to 2% of the output
voltage. But if the selected capacitor’s ESR is extremely low
(below 0.05
W), there is a possibility of an unstable feedback
loop, resulting in oscillation at the output. This situation can
occur when a tantalum capacitor, that can have a very low
ESR, is used as the only output capacitor.
At Low Temperatures, Put in Parallel Aluminium
Electrolytic Capacitors with Tantalum Capacitors
Electrolytic capacitors are not recommended for
temperatures below 25
°C. The ESR rises dramatically at
cold temperatures and typically rises 3 times at 25
°C and
as much as 10 times at 40
°C. Solid tantalum capacitors
have much better ESR spec at cold temperatures and are
recommended for temperatures below 25
°C. They can be
also used in parallel with aluminium electrolytics. The value
of the tantalum capacitor should be about 10% or 20% of the
total capacitance. The output capacitor should have at least
50% higher RMS ripple current rating at 52 kHz than the
peaktopeak inductor ripple current.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2576T-12-H | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Voltage-Mode SMPS Controller |
| LM2576T-12LB03 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Voltage-Mode SMPS Controller |
| LM2576T-12P | 制造商:National Semiconductor Corporation 功能描述:2576T-12 制造商:Texas Instruments 功能描述:2576T-12 |
| LM2576T-12-V | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Voltage-Mode SMPS Controller |
| LM2576T-15 | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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