欢迎访问ic37.com |
会员登录 免费注册
发布采购

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 ]
 浏览型号LM2576-ADJ的Datasheet PDF文件第7页浏览型号LM2576-ADJ的Datasheet PDF文件第8页浏览型号LM2576-ADJ的Datasheet PDF文件第9页浏览型号LM2576-ADJ的Datasheet PDF文件第10页浏览型号LM2576-ADJ的Datasheet PDF文件第12页浏览型号LM2576-ADJ的Datasheet PDF文件第13页浏览型号LM2576-ADJ的Datasheet PDF文件第14页浏览型号LM2576-ADJ的Datasheet PDF文件第15页  
LM2576  
Procedure (Fixed Output Voltage Version) (continued)In order to simplify the switching regulator design, a step–by–step  
design procedure and some examples are provided.  
Procedure  
Example  
5. Output Capacitor Selection (C  
)
5. Output Capacitor Selection (C  
)
out  
out  
= 680 µF to 2000 µF standard aluminium electrolytic.  
A. Since the LM2576 is a forward–mode switching regulator  
with voltage mode control, its open loop 2–pole–1–zero  
frequency characteristic has the dominant pole–pair  
determined by the output capacitor and inductor values. For  
stable operation and an acceptable ripple voltage,  
(approximately 1% of the output voltage) a value between  
680 µF and 2000 µF is recommended.  
A. C  
out  
B. Due to the fact that the higher voltage electrolytic capacitors  
generally have lower ESR (Equivalent Series Resistance)  
numbers, the output capacitor’s voltage rating should be at  
least 1.5 times greater than the output voltage. For a 5.0 V  
regulator, a rating at least 8.0 V is appropriate, and a 10 V or  
16 V rating is recommended.  
B. Capacitor voltage rating = 20 V.  
Procedure (Adjustable Output Version: LM2576–ADJ)  
Procedure  
Example  
Given Parameters:  
Given Parameters:  
V
= Regulated Output Voltage  
V
= 8.0 V  
out  
out  
V
I
= Maximum DC Input Voltage  
= Maximum Load Current  
V
I
= 25 V  
= 2.5 A  
in(max)  
in(max)  
Load(max)  
Load(max)  
1. Programming Output Voltage  
1. Programming Output Voltage (selecting R1 and R2)  
To select the right programming resistor R1 and R2 value (see  
Figure 2) use the following formula:  
Select R1 and R2:  
R2  
R1  
V
1.23 1.0  
Select R1 = 1.8 kΩ  
out  
R2  
R1  
V
V
1.0  
where V = 1.23 V  
ref  
out  
ref  
V
out  
8.0 V  
1.8 k  
R2  
R1  
1.0  
1.0  
Resistor R1 can be between 1.0 k and 5.0 k. (For best  
temperature coefficient and stability with time, use 1% metal  
film resistors).  
V
1.23 V  
ref  
R2 = 9.91 k, choose a 9.88 k metal film resistor.  
V
out  
R2  
R1  
– 1.0  
V
ref  
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, 150 V aluminium electrolytic capacitor located near  
the input and ground pin 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.  
For additional information see input capacitor section in the  
“Application Hints” section of this data sheet.  
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, a 3.0 A current rating is adequate.  
B. Use a 30 V 1N5821 Schottky diode or any  
suggested fast recovery diode in the Table 1.  
11  
MOTOROLA ANALOG IC DEVICE DATA