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LM2594M-ADJ 参数 Datasheet PDF下载

LM2594M-ADJ图片预览
型号: LM2594M-ADJ
PDF下载: 下载PDF文件 查看货源
内容描述: SIMPLE SWITCHER系列电源转换器150千赫0.5A降压稳压器 [SIMPLE SWITCHER Power Converter 150 kHz 0.5A Step-Down Voltage Regulator]
分类和应用: 转换器稳压器开关式稳压器或控制器电源电路开关式控制器光电二极管PC
文件页数/大小: 28 页 / 742 K
品牌: NSC [ National Semiconductor ]
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LM2594/LM2594HV Series Buck Regulator Design Procedure (Fixed  
Output)  
PROCEDURE (Fixed Output Voltage Version)  
EXAMPLE (Fixed Output Voltage Version)  
Given:  
Given:  
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VOUT 5V  
VOUT Regulated Output Voltage (3.3V, 5V or 12V)  
=
=
VIN(max) 12V  
VIN(max) Maximum DC Input Voltage  
=
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ILOAD(max) Maximum Load Current  
ILOAD(max) 0.4A  
1. Inductor Selection (L1)  
1. Inductor Selection (L1)  
A. Select the correct inductor value selection guide from Fig-  
ures 4, 5 or Figure 6. (Output voltages of 3.3V, 5V, or 12V re-  
spectively.) For all other voltages, see the design procedure  
for the adjustable version.  
A. Use the inductor selection guide for the 5V version shown  
in Figure 5.  
B. From the inductor value selection guide shown in Figure 5,  
the inductance region intersected by the 12V horizontal line  
and the 0.4A vertical line is 100 µH, and the inductor code is  
L20.  
B. From the inductor value selection guide, identify the induc-  
tance region intersected by the Maximum Input Voltage line  
and the Maximum Load Current line. Each region is identified  
by an inductance value and an inductor code (LXX).  
C. The inductance value required is 100 µH. From the table  
in Figure 8, go to the L20 line and choose an inductor part  
number from any of the four manufacturers shown. (In most  
instance, both through hole and surface mount inductors are  
available.)  
C. Select an appropriate inductor from the four manufactur-  
er’s part numbers listed in Figure 8.  
2. Output Capacitor Selection (COUT  
)
2. Output Capacitor Selection (COUT)  
A. In the majority of applications, low ESR (Equivalent Series  
Resistance) electrolytic capacitors between 82 µF and  
220 µF and low ESR solid tantalum capacitors between 15  
µF and 100 µF provide the best results. This capacitor should  
be located close to the IC using short capacitor leads and  
short copper traces. Do not use capacitors larger than  
220 µF.  
A. See section on output capacitors in application infor-  
mation section.  
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 0.5A line. In the maximum input voltage column, select  
the line that covers the input voltage needed in your applica-  
tion, in this example, use the 15V line. Continuing on this line  
are recommended inductors and capacitors that will provide  
the best overall performance.  
For additional information, see section on output capaci-  
tors in application information section.  
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 ca-  
pacitors that will provide the best design solutions.  
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.  
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.  
In this example aluminum electrolytic capacitors from several  
different manufacturers are available with the range of ESR  
numbers needed.  
D. For computer aided design software, see Switchers Made  
Simple version 4.1 or later.  
120 µF 25V Panasonic HFQ Series  
120 µF 25V Nichicon PL Series  
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, 120 µF 10V aluminum electrolytic capacitor  
would exhibit approximately 400 mof ESR (see the curve  
in Figure 14 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 ca-  
pacitor with a higher voltage rating (lower ESR) should be se-  
lected. A 16V or 25V capacitor will reduce the ripple voltage  
by approximately half.  
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