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SS23 参数 Datasheet PDF下载

SS23图片预览
型号: SS23
PDF下载: 下载PDF文件 查看货源
内容描述: 2A , 380千赫降压转换器 [2A, 380 KHz Step-Down Converter]
分类和应用: 转换器二极管光电二极管
文件页数/大小: 10 页 / 249 K
品牌: MPS [ MONOLITHIC POWER SYSTEMS ]
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TM  
MP1580 – 2A, 380KHz STEP-DOWN CONVERTER  
Input Capacitor  
In the case of tantalum or low-ESR electrolytic  
capacitors, the ESR dominates the impedance  
at the oscillator frequency, therefore the output  
ripple is calculated as:  
The input current to the step-down converter is  
discontinuous, so a capacitor is required to  
supply the AC current to the step-down  
converter while maintaining the DC input  
voltage. A low ESR capacitor is required to  
keep the noise at the IC to a minimum. Ceramic  
capacitors are preferred, but tantalum or low-  
ESR electrolytic capacitors will also suffice.  
VRIPPLE ≅ ∆I×RESR  
Where VRIPPLE is the output voltage ripple and  
RESR is the equivalent series resistance of the  
output capacitors.  
The input capacitor value should be greater  
than 10µF. The capacitor can be electrolytic,  
tantalum or ceramic. However, since it absorbs  
the input switching current it requires an  
adequate ripple current rating. Its RMS current  
rating should be greater than approximately 1/2  
of the DC load current.  
Output Rectifier Diode  
The output rectifier diode supplies the current to  
the inductor when the upper transistor M1 is off.  
To reduce losses due to the diode forward  
voltage and recovery times, use a Schottky  
rectifier.  
Table 2 provides the Schottky rectifier part  
numbers based on the maximum input voltage  
and current rating.  
To ensure stable operation, C1 should be  
placed as close to the IN pin as possible.  
Alternately, a smaller high quality ceramic  
0.1µF capacitor may be placed closer to the IN  
pin and a larger capacitor placed further away.  
If using this technique, it is recommended that  
the larger capacitor be a tantalum or electrolytic  
type capacitor. All ceramic capacitors should be  
placed close to the MP1580.  
Table 2—Schottky Rectifier Selection Guide  
2A Load Current  
VIN (Max)  
Part Number  
30BQ015  
B220  
Vendor  
15V  
20V  
4
1
Output Capacitor  
SK23  
6
The output capacitor is required to maintain the  
DC output voltage. Low ESR capacitors are  
preferred to keep the output voltage ripple low.  
The characteristics of the output capacitor also  
affect the stability of the regulation control  
system. Ceramic, tantalum or low ESR  
electrolytic capacitors are recommended. In the  
case of ceramic capacitors, the impedance at  
the oscillator frequency is dominated by the  
capacitance, so the output voltage ripple is  
mostly independent of the ESR. The output  
voltage ripple is estimated to be:  
SR22  
6
20BQ030  
B230  
4
1
26V  
SK23  
6
SR23  
3, 6  
2, 3  
SS23  
Table 3 lists some rectifier manufacturers.  
Table 3—Schottky Diode Manufacturers  
Vendor  
Web Site  
2
Diodes, Inc.  
www.diodes.com  
f
LC  
VRIPPLE 1.4 × VIN  
×
Fairchild Semiconductor www.fairchildsemi.com  
General Semiconductor www.gensemi.com  
f
Where VRIPPLE is the output ripple voltage, fLC is  
the resonant frequency of the LC filter and f is  
the oscillator frequency.  
International Rectifier  
On Semiconductor  
Pan Jit International  
www.irf.com  
www.onsemi.com  
www.panjit.com.tw  
Choose a rectifier that has a maximum reverse  
voltage rating greater than the maximum input  
voltage, and a current rating greater than the  
maximum load current.  
MP1580 Rev. 3.0  
12/5/2005  
www.MonolithicPower.com  
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.  
© 2005 MPS. All Rights Reserved.  
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