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SC420AIMLTRT 参数 Datasheet PDF下载

SC420AIMLTRT图片预览
型号: SC420AIMLTRT
PDF下载: 下载PDF文件 查看货源
内容描述: 高速,组合式SenseTM ,为移动应用程序同步功率MOSFET驱动器 [High Speed, Combi-SenseTM, Synchronous Power MOSFET Driver for Mobile Applications]
分类和应用: 驱动器
文件页数/大小: 16 页 / 744 K
品牌: SEMTECH [ SEMTECH CORPORATION ]
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SC420A  
POWER MANAGEMENT  
Applications Information (Cont.)  
Top Gate Resistor (Rtg)  
COMPONENT SELECTION FOR SC420A APPLICATION:  
TG resistance is not generally required, as Rbst can take  
care of the rising edge. We recommend one Rtg for each  
HSFET only when the maximum length of the TG trace > 2  
inches. Populate with 0 initially.  
High Side MOSFET (LSFET)  
The SC420A is usually used for low duty cycle ( ~ 10% )  
applications. So the Rds (ON) of the high side MOSFET is  
not a parameter of significant importance. A 10 – 25  
mÙ Rds for the HSFET is acceptable depending on the  
load current. Minimum Qg for the HSFET is important for  
component selection. Typical range is 10 – 25 nC.  
Boost Diode (Dbst)  
Boost Diode as shown in the above figure is required and  
should have a very low forward voltage drop. This increases  
the amount of charge on Cbst capacitor.  
Low Side MOSFET (LSFET)  
Rds is the critical selection parameter for LSFET. IT should  
be as low as possible for reduction of conduction losses  
and hence increase efficiency. Typical range is 1 – 3 mÙ.  
Rg is another important parameter for LSFET. It should  
be as low as possible as this will give better efficiency.  
Typical range 0.1 – 2 . Ratio of Qgd/Qgs is third  
parameter of consideration.  
Delay Capacitor (Cdly)  
Delay capacitor is not added in a typical application. This  
option is useful to control the delay between the BG falling  
and TG rising edges. Cdly is used for very high capacitance  
LSFETs to ensure BG is below Vth of the FET before TG  
turns on.  
As the duty cycle for the application increases, require-  
ments for the two FETs become more similar; however,  
switching charge will always be more important to the  
HSFET since it switches into the full voltage, and the LSFET  
always switching into the near zero voltage.  
Decoupling capacitors (C1,C3)  
These are de-coupling capacitors present in the circuit.  
Place as close to SC420A as possible. Typical rating is 1uF/  
10V for C1 and 0.1uF /25V for C3.  
Boost Capacitor (Cbst)  
Boost capacitor is important for SC420A application as  
shown in the above figure. It is a good design rule to have  
boost capacitance at least 100 X the Cgs for the HSFET.  
Boost Resistor (Rbst)  
Boost resistance is important and depends on the layout.  
We recommend always designing with the resistor as shown  
in the above circuit to help minimize EMI when the HSFET  
turns on. The value required is layout dependant.  
Bottom Gate Resistor (Rbg)  
BG resistance is normally not required, but may be needed  
for damping for long BG trace runs. We recommend one  
Rbg for each LSFET only when the maximum length of the  
BG trace is > 1 inch. Populate with 0 initially.  
2004 Semtech Corp.  
11  
United States Patent No. 6,441,597  
www.semtech.com