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LM2576-ADJ 参数 Datasheet PDF下载

LM2576-ADJ图片预览
型号: LM2576-ADJ
PDF下载: 下载PDF文件 查看货源
内容描述: 轻松切换3.0A降压稳压器 [Easy Switcher 3.0A Step-Down Voltage Regulator]
分类和应用: 稳压器
文件页数/大小: 28 页 / 288 K
品牌: MOTOROLA [ MOTOROLA ]
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LM2576  
Procedure (Fixed Output Voltage Version) In order to simplify the switching regulator design, a step–by–step  
design procedure and some examples are provided.  
Procedure  
Example  
Given Parameters:  
= Regulated Output Voltage (3.3 V, 5.0 V, 12 V or 15 V)  
Given Parameters:  
= 5.0 V  
V
out  
V
out  
V
I
= Maximum Input Voltage  
= Maximum Load Current  
V
I
= 15 V  
= 3.0 A  
in(max)  
in(max)  
Load(max)  
Load(max)  
1. Controller IC Selection  
1. Controller IC Selection  
According to the required input voltage, output voltage and  
current, select the appropriate type of the controller IC output  
voltage version.  
According to the required input voltage, output voltage, current  
polarity and current value, use the LM2576–5 controller IC  
2. Input Capacitor Selection (C  
)
2. Input Capacitor Selection (C )  
in  
in  
To prevent large voltage transients from appearing at the input  
and for stable operation of the converter, an aluminium or  
tantalum electrolytic bypass capacitor is needed between the  
A 100 µF, 25 V aluminium electrolytic capacitor located near to  
the input and ground pins provides sufficient bypassing.  
input pin +V and ground pin Gnd. This capacitor should be  
in  
located close to the IC using short leads. This capacitor should  
have a low ESR (Equivalent Series Resistance) value.  
3. Catch Diode Selection (D1)  
3. Catch Diode Selection (D1)  
A. Since the diode maximum peak current exceeds the  
regulator maximum load current the catch diode current  
rating must be at least 1.2 times greater than the maximum  
load current. For a robust design the diode should have a  
current rating equal to the maximum current limit of the  
LM2576 to be able to withstand a continuous output short  
B. The reverse voltage rating of the diode should be at least  
1.25 times the maximum input voltage.  
A. For this example the current rating of the diode is 3.0 A.  
B. Use a 20 V 1N5820 Schottky diode, or any of the suggested  
fast recovery diodes shown in Table 1.  
4. Inductor Selection (L1)  
4. Inductor Selection (L1)  
A. According to the required working conditions, select the  
correct inductor value using the selection guide from  
Figures 18 to 22.  
A. Use the inductor selection guide shown in Figures 19.  
B. From the appropriate inductor selection guide, identify the  
inductance 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.  
B. From the selection guide, the inductance area intersected  
by the 15 V line and 3.0 A line is L100.  
C. Select an appropriate inductor from the several different  
manufacturers part numbers listed in Table 2.  
The designer must realize that the inductor current rating  
must be higher than the maximum peak current flowing  
through the inductor. This maximum peak current can be  
calculated as follows:  
C. Inductor value required is 100 µH. From Table 2, choose  
an inductor from any of the listed manufacturers.  
V
–V  
t
on  
out  
2L  
in  
I
I
Load(max)  
p(max)  
where t is the “on” time of the power switch and  
on  
V
out  
1.0  
t
x
on  
V
f
osc  
in  
For additional information about the inductor, see the  
inductor section in the “Application Hints” section of  
this data sheet.  
10  
MOTOROLA ANALOG IC DEVICE DATA