参数资料
型号: LM2674-5.0MWC
厂商: NATIONAL SEMICONDUCTOR CORP
元件分类: 稳压器
英文描述: 1.25 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, UUC
封装: WAFER
文件页数: 3/31页
文件大小: 596K
代理商: LM2674-5.0MWC
LM2674 Series Buck Regulator Design Procedure (Fixed Output) (Continued)
PROCEDURE (Fixed Output Voltage Version)
EXAMPLE (Fixed Output Voltage Version)
The capacitor list contains through-hole electrolytic capacitors
from four different capacitor manufacturers and surface mount
tantalum capacitors from two different capacitor manufacturers.
It is recommended that both the manufacturers and the
manufacturer’s series that are listed in the table be used. A
table listing the manufacturers’ phone numbers is located in
Surface Mount:
68 F/10V
Sprague 594D Series.
100 F/10V
AVX TPS Series.
Through Hole:
68 F/10V
Sanyo OS-CON SA Series.
150 F/35V
Sanyo MV-GX Series.
150 F/35V
Nichicon PL Series.
150 F/35V
Panasonic HFQ Series.
3. Catch Diode Selection (D1)
A. In normal operation, the average current of the catch diode is
the load current times the catch diode duty cycle, 1-D (D is the
switch duty cycle, which is approximately the output voltage
divided by the input voltage). The largest value of the catch
diode average current occurs at the maximum load current and
maximum input voltage (minimum D). For normal operation, the
catch diode current rating must be at least 1.3 times greater
than its maximum average current. However, 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 LM2674. The most stressful condition for this diode is a
shorted output condition.
3. Catch Diode Selection (D1)
A. Refer to the table shown in Figure 12. In this example, a 1A,
20V Schottky diode will provide the best performance. If the
circuit must withstand a continuous shorted output, a higher
current Schottky diode is recommended.
B. The reverse voltage rating of the diode should be at least
1.25 times the maximum input voltage.
C. Because of their fast switching speed and low forward
voltage drop, Schottky diodes provide the best performance and
efficiency. This Schottky diode must be located close to the
LM2674 using short leads and short printed circuit traces.
4. Input Capacitor (C
IN)
4. Input Capacitor (C
IN)
LM2674
www.national.com
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