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TPS62402短路电流不正常

Other Parts Discussed in Thread: TPS62402

hi,

使用TPS62402,5V to 3.3V/600mA and 1.8V/400mA,DEMO原理图如下:

pcb如下:

当芯片正常运行后,将输出端短路,波形如下:

ch1 电感电流  ch3 SW点电压

将输出端短路后,然后上电,波形为:

ch1 电感电流  ch3 SW点电压

从上面测试波形来看:不管是在线短路,还是短路开机,波形都不对,只是短路开机波形看起来更严重些。

根据datasheet,所期望的OCP保护机制为,PMOS触发峰值过流保护点后关断,然后NMOS导通,直到NMOS的电流低于谷值电流保护点后PMOS才能导通。

请大家帮忙分析分析,非常感谢!