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參數資料
| 型號： | LM2598T-12 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩壓器 |
| 英文描述： | SIMPLE SWITCHER Power Converter 150 kHz 1A Step-Down Voltage Regulator, with Features |
| 中文描述： | 2.6 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, PSFM7 |
| 封裝： | BENT STAGGERED, TO-220, 7 PIN |
| 文件頁數： | 11/33頁 |
| 文件大小： | 847K |
| 代理商： | LM2598T-12 |
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LM2598 Series Buck Regulator Design Procedure (Fixed Output)
(Continued)
PROCEDURE (Fixed Output Voltage Version)
EXAMPLE (Fixed Output Voltage Version)
B.
To simplify the capacitor selection procedure, refer to the
quick design component selection table shown in Figure 2
This table contains different input voltages, output voltages,
and load currents, and lists various inductors and output
capacitors that will provide the best design solutions.
B.
From the quick design component selection table shown
in Figure 2 locate the 5V output voltage section. In the load
current column, choose the load current line that is closest to
the current needed in your application, for this example, use
the 1A line. In the maximum input voltage column, select the
line that covers the input voltage needed in your application,
in this example, use the 15V line. Continuing on this line are
recommended inductors and capacitors that will provide the
best overall performance.
The capacitor list contains both through hole electrolytic and
surface mount tantalum capacitors from four different capaci-
tor manufacturers. It is recommended that both the manufac-
turers and the manufacturer’s series that are listed in the
table be used.
In this example aluminum electrolytic capacitors from several
different manufacturers are available with the range of ESR
numbers needed.
220 μF
25V
Panasonic HFQ Series
220 μF
25V
Nichicon PL Series
C.
The capacitor voltage rating for electrolytic capacitors
should be at least 1.5 times greater than the output voltage,
and often much higher voltage ratings are needed to satisfy
the low ESR requirements for low output ripple voltage .
C.
For a 5V output, a capacitor voltage rating at least 7.5V or
more is needed. But, in this example, even a low ESR,
switching grade, 220 μF 10V aluminum electrolytic capacitor
would exhibit approximately 225 m
of ESR (see the curve
in Figure 17 for the ESR vs voltage rating). This amount of
ESR would result in relatively high output ripple voltage. To
reduce the ripple to 1% of the output voltage, or less, a
capacitor with a higher voltage rating (lower ESR) should be
selected. A 16V or 25V capacitor will reduce the ripple volt-
age by approximately half.
D.
For computer aided design software, see Switchers Made
Simple
(version 4.2 or later).
3. Catch Diode Selection (D1)
3. Catch Diode Selection (D1)
A.
The catch diode current rating must be at least 1.3 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 LM2598. The most stressful condition for
this diode is an overload or shorted output condition.
A.
Refer to the table shown in Figure 11 In this example, a
3A, 20V, 1N5820 Schottky diode will provide the best perfor-
mance, and will not be overstressed even for a shorted
output.
B.
The reverse voltage rating of the diode should be at least
1.25 times the maximum input voltage.
C.
This diode must be fast (short reverse recovery time) and
must be located close to the LM2598 using short leads and
short printed circuit traces. Because of their fast switching
speed and low forward voltage drop, Schottky diodes provide
the best performance and efficiency, and should be the first
choice, especially in low output voltage applications.
Ultra-fast recovery, or High-Efficiency rectifiers also provide
good results. Ultra-fast recovery diodes typically have re-
verse recovery times of 50 ns or less. Rectifiers such as the
1N5400 series are much too slow and should not be used.
L
www.national.com
11
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LM2598T-12/NOPB | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| LM2598T-3.3 | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| LM2598T-3.3/NOPB | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| LM2598T-5.0 | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| LM2598T-5.0/NOPB | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
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