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AS1341_1 参数 Datasheet PDF下载

AS1341_1图片预览
型号: AS1341_1
PDF下载: 下载PDF文件 查看货源
内容描述: 20V , 600毫安, 100 %占空比,降压型转换器 [20V, 600mA, 100% Duty Cycle, Step-Down Converter]
分类和应用: 转换器
文件页数/大小: 17 页 / 926 K
品牌: AMSCO [ AMS(艾迈斯) ]
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AS1341  
Datasheet - Application Information  
Setting Current Limit  
The AS1341 adjustable peak current limit is set by connecting ILIMIT as shown in Table 4.  
Table 4. Setting Peak Current Limit  
Current Limit  
700mA  
ILIMIT Connected To  
GND  
IN  
1400mA  
The current limit chosen should reflect the maximum load current. The maximum output current is half of the peak cur-  
rent limit. Choosing a lower current limit allows using an inductor with a lower current rating, however, it requires a  
higher inductance (see Inductor Selection) and does not allow for reduced inductor package size.  
Inductor Selection  
The AS1341 operates with a wide range of inductance values. For most applications, values between 10µH and 47µH  
work best with the controller’s high switching frequency. Larger inductor values will reduce the switching frequency and  
thereby improve efficiency and EMI.  
Note: The four key factors in inductor selection are inductance value, saturation rating, series resistance, and size.  
The trade-off for improved efficiency is a higher output ripple and slower transient response. On the other hand, low-  
value inductors respond faster to transients, improve output ripple, offer smaller physical size, and minimize cost. If the  
inductor value is too small, the peak inductor current exceeds the current limit due to current-sense comparator propa-  
gation delay, potentially exceeding the inductor’s current rating. Calculate the minimum inductance value as follows:  
LMIN = ((VINMAX - VOUTPUT) x tONMIN/ILXPEAK  
(EQ 3)  
Where:  
tONMIN = 1µs  
The inductor saturation current rating must be greater than the peak switch current limit, plus the overshoot due to the  
250ns current-sense comparator propagation delay. Saturation occurs when the magnetic flux density of the inductor  
reaches the maximum level the core can support and the inductance starts to fall. Choose an inductor with a saturation  
rating greater than IPEAK in the following equation:  
IPEAK = (ILXPEAK + (VIN - VOUTPUT) x 250ns)/L  
(EQ 4)  
Inductor series resistance affects both efficiency and dropout voltage (see Dropout Voltage on page 9). High series  
resistance limits the maximum current available at lower input voltages, and increases the dropout voltage. For opti-  
mum performance, select an inductor with the lowest possible DC resistance that fits in the allotted dimensions.  
Table 5. Recommended Inductors  
Part Number  
L
DCR  
Current Rating  
1.4A  
Manufacturer  
Coilcraft  
www.coilcraft.com  
MSS6132-103ML  
LPS4018-472ML  
MSS6132-393ML  
LPS4018-223ML  
CDRH6D28NP-150  
CDRH5D18NP-4R1  
CDRH6D28NP-470  
CDRH5D18NP-220  
LQH66SN-100M03  
LQH55DN-150M03  
LQH66SN-470M03  
LQH55DN-470M03  
10µH  
4.7µH  
39µH  
22µH  
15µH  
4.1µH  
47µH  
22µH  
10µH  
15µH  
47µH  
47µH  
85mΩ  
125mΩ  
345mΩ  
360mΩ  
62mΩ  
1.8A  
0.8A  
0.7A  
Sumida  
www.sumida.com  
1.4A  
57mΩ  
1.95A  
0.8A  
176mΩ  
215mΩ  
36mΩ  
0.8A  
Murata  
www.murata.com  
1.6A  
150mΩ  
170mΩ  
400mΩ  
1.4A  
0.8A  
0.8A  
www.austriamicrosystems.com  
Revision 1.05  
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