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RT7262E 参数 Datasheet PDF下载

RT7262E图片预览
型号: RT7262E
PDF下载: 下载PDF文件 查看货源
内容描述: 2A , 21V 500kHz的同步降压型转换器 [2A, 21V 500kHz Synchronous Step-Down Converter]
分类和应用: 转换器TI的电源Demo板
文件页数/大小: 17 页 / 380 K
品牌: RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
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RT7262E  
then recover automatically. The Hiccup Mode of UVP can  
reduce input current in short-circuit conditions.  
Table 2. Suggested Inductors for Typical  
Application Circuit  
Component Supplier  
Series  
Dimensions (mm)  
10 x 9.7 x 4.5  
Inductor Selection  
TDK  
TDK  
VLF10045  
For a given input and output voltage, the inductor value  
and operating frequency determine the ripple current. The  
ripple current ΔIL increases with higher VIN and decreases  
with higher inductance.  
SLF12565 12.5 x 12.5 x 6.5  
NR8040 8 x 8 x 4  
TAIYO YUDEN  
Input and Output Capacitors Selection  
V
f ×L  
VOUT  
V
IN  
OUT ⎤ ⎡  
× 1−  
⎥ ⎢  
ΔIL =  
⎦ ⎣  
The input capacitance, CIN, is needed to filter the  
trapezoidal current at the source of the high side MOSFET.  
To prevent large ripple current, a low ESR input capacitor  
sized for the maximum RMS current should be used. The  
RMS current is given by :  
Having a lower ripple current reduces not only the ESR  
losses in the output capacitors but also the output voltage  
ripple. Highest efficiency operation is achieved by reducing  
ripple current at low frequency, but it requires a large  
inductor to attain this goal.  
V
V
V
IN  
V
OUT  
OUT  
I
= I  
1  
RMS  
OUT(MAX)  
IN  
For the ripple current selection, the value of ΔIL = 0.24(IMAX  
)
This formula has a maximum at VIN = 2VOUT, where IRMS  
=
will be a reasonable starting point. The largest ripple current  
occurs at the highest VIN. To guarantee that the ripple  
current stays below a specified maximum, the inductor  
value should be chosen according to the following  
equation :  
I
/ 2. This simple worst case condition is commonly  
OUT  
used for design because even significant deviations do  
not offer much relief.  
Choose a capacitor rated at a higher temperature than  
required. Several capacitors may also be paralleled to  
meet size or height requirements in the design.  
⎤ ⎡  
V
OUT  
V
OUT  
L =  
× 1−  
⎥ ⎢  
f × ΔI  
V
IN(MAX)  
L(MAX)  
⎦ ⎣  
The inductor's current rating (caused a 40°C temperature  
rising from 25°C ambient) should be greater than the  
maximum load current and its saturation current should  
be greater than the short circuit peak current limit. Please  
see Table 2 for the inductor selection reference and it is  
highly recommended to keep inductor value as close as  
possible to the recommended inductor values for each  
Vout as shown in Table 1.  
For the input capacitor, one 22μF low ESR ceramic  
capacitors are recommended. For the recommended  
capacitor, please refer to Table 3 for more detail.  
Table 3. Suggested Capacitors for CIN and COUT  
Location  
CIN  
Component Supplier  
MURATA  
TDK  
Part No.  
Capacitance (μF)  
Case Size  
1210  
GRM32ER71C226M  
C3225X5R1C226M  
GRM31CR60J476M  
C3225X5R0J476M  
GRM32ER71C226M  
C3225X5R1C226M  
22  
22  
47  
47  
22  
22  
CIN  
1210  
COUT  
COUT  
COUT  
COUT  
MURATA  
TDK  
1206  
1210  
MURATA  
TDK  
1210  
1210  
Copyright 2012 Richtek Technology Corporation. All rights reserved.  
©
is a registered trademark of Richtek Technology Corporation.  
DS7262E-00 November 2012  
www.richtek.com  
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