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參數(shù)資料
| 型號： | LM2576-12MWC |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 7.5 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, UUC |
| 封裝： | WAFER |
| 文件頁數(shù)： | 5/27頁 |
| 文件大?。?/td> | 741K |
| 代理商： | LM2576-12MWC |
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LM2576 Series Buck Regulator Design Procedure (Continued)
PROCEDURE (Adjustable Output Voltage Versions)
EXAMPLE (Adjustable Output Voltage Versions)
2. Inductor Selection (L1)
A. Calculate the inductor Volt
microsecond constant,
E
T(V
s),
from
the
following
formula:
B. Use the E
T value from the previous formula and
match it with the E
T number on the vertical axis of the
Inductor Value Selection Guide shown in
Figure 7.
C. On the horizontal axis, select the maximum load cur-
rent.
D. Identify the inductance region intersected by the E
T
value and the maximum load current value, and note the
inductor code for that region.
E. Identify the inductor value from the inductor code, and
select an appropriate inductor from the table shown in
Figure 9. Part numbers are listed for three inductor manu-
facturers. The inductor chosen must be rated for opera-
tion at the LM2576 switching frequency (52 kHz) and for a
current rating of 1.15 x I
LOAD. For additional inductor in-
formation, see the inductor section in the application hints
section of this data sheet.
2. Inductor Selection (L1)
A. Calculate E
T(V s)
B. E
T = 115 V s
C. I
LOAD(Max) = 3A
D. Inductance Region = H150
E. Inductor Value = 150 H
Choose from AIE part
#415-0936 Pulse Engineering part #PE-531115, or
Renco part #RL2445.
3. Output Capacitor Selection (C
OUT)
A. The value of the output capacitor together with the in-
ductor defines the dominate pole-pair of the switching
regulator loop. For stable operation, the capacitor must
satisfy the following requirement:
The above formula yields capacitor values between 10 F
and 2200 F that will satisfy the loop requirements for
stable operation. But to achieve an acceptable output
ripple voltage, (approximately 1% of the output voltage)
and transient response, the output capacitor may need to
be several times larger than the above formula yields.
B. The capacitor’s voltage rating should be at last 1.5
times greater than the output voltage. For a 10V regulator,
a rating of at least 15V or more is recommended. Higher
voltage electrolytic capacitors generally have lower ESR
numbers, and for this reason it may be necessary to se-
lect a capacitor rate for a higher voltage than would nor-
mally be needed.
3. Output Capacitor Selection (C
OUT)
However, for acceptable output ripple voltage select
C
OUT ≥ 680 F
C
OUT = 680 F electrolytic capacitor
4. Catch Diode Selection (D1)
A. The catch-diode current rating must be at least 1.2
times greater than the maximum load current. Also, if the
power supply design must withstand a continuous output
short, the diode should have a current rating equal to the
maximum current limit of the LM2576. The most stressful
condition for this diode is an overload or shorted output.
See diode selection guide in
Figure 8.
B. The reverse voltage rating of the diode should be at
least 1.25 times the maximum input voltage.
4. Catch Diode Selection (D1)
A. For this example, a 3.3A current rating is adequate.
B. Use a 30V 31DQ03 Schottky diode, or any of the sug-
gested fast-recovery diodes in
Figure 8.
5. Input Capacitor (C
IN)
An aluminum or tantalum electrolytic bypass capacitor lo-
cated close to the regulator is needed for stable opera-
tion.
5. Input Capacitor (C
IN)
A 100 F aluminum electrolytic capacitor located near the
input and ground pins provides sufficient bypassing.
www.national.com
13
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| LM2576-12WT | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3A Step-Down SMPS Regulator (ROHS Compliant) 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM2576-12WU | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3A Step-Down SMPS Regulator (ROHS Compliant) 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM2576-12WU TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3A Step-Down SMPS Regulator (ROHS Compliant) 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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