路过的进来看看、、、器件的选择问题

请铭记

Hi：U13就是相当于一个Nmos开关的作用，不明白为什么不直接用NMOS器件，成本不是吧？还是说USB电源这块有什么特殊的要求吗？小弟不太明白，求粮、、、、thanks！

Vincent.M

USB供电电路这用过两种：MOSFET做USB供电开关用；用专用的可设置限流值的开关芯片，如SIP4610。
RT9701看起来这里用来实现两个目的：
* L2 J# F) r* p! t1、A built-in charge pump is used to drive the N-Channel MOSFET that is free of parasitic body diode to eliminate any reversed current flow across the switch when it is powered off——区别于mosfet，无寄生的并联二极管，防止反向电流
: Y  M3 y- f3 n, r9 n3 S! O0 q& E2、The current limit threshold is set internally to allow a minimum of 1.1A through the MOSFET but limits the output current to approximately 1.5A typical——固定值1.5A限流

lxizj

不一样哦，用MOS FET做的，算是负载开关。而RT9701是限流开关。

kaka198510

限流的作用,USB一般会限制在500ma和900ma

超級狗

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kaka198510 发表于 2013-7-11 09:59
限流的作用,USB一般会限制在500ma和900ma

Richtek RT9701
Several protection functions include soft start to limit inrush current during plug-in, current limiting at 1.5A to meet USB power requirement, and thermal shutdown to protect damage under over current conditions.
7 M" _1 v& p! [5 h
可以不放，就看你在不在意這些問題，還有認證過不過得了。

{:soso_e144:}
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请铭记

超級狗 发表于 2013-7-11 11:24
( i1 j; W! b. H& i3 S5 r! d5 ^4 K% ORichtek RT9701
Several protection functions include soft start to limit inrush current during plu ...

THANKS