PMP4486: INA286

In this reference design schematic, which can be found at https://www.ti.com.cn/cn/lit/df/tidrp75/tidrp75.pdf?ts=1622029946679ref_url=https%253A%252F%252Fwww.ti.com.cn%252Ftool%252Fcn%252FPMP4486%253FkeyMatch%253D%2526tisearch%253Dsearch-everything%2526usecase%253Drefdesign

l cannot figure out the principles of the ouput current sense of the Buck converter. In this circuit,  The resistor R33 and capacitor C51 are in parallel with the Buck inductor. Then the voltage between R32 is connected with the input of operational amplifier INA286. Then the output of the INA286 is the output current sensing signal.

My question is as follow:

1. n this circuit, l think the voltage between the Buck inductor L5 can not reflect the output current information. Why this circuit can realize the funciton of output current sense?

2. The frequency of input signal of INA286 is same as the switching frequency of Buck converter, which is 800kHz. But the bandwidth of INA286 is not enough to transfer the input signal. Where l am wrong?

Looking forward to your instruction. Thank you.

Johnsin Tao：

Hi

     这个电路类似于一些纹波取样，或者电流保护，在TI的DC/DC芯片中偶尔会用到这个电路，不过大部分前者使用电容ESR或者串联小电阻，后者是采用sense电阻甚至MOS导通Rdson.

      这款运放常见应用是监测电流，你可以在“放大器”对应论坛问一下关于带宽的问题。

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jake sun：

你好，这个电路是不是只能用于过流保护，而无法实现输出电流采样功能？当发生短路的时候，电感电流快速上升，电感两端电压很大，进而传递到运放的输出端，经过比较器可以做保护，这个可以理解。但是，仅依靠电感电压信息，我想不到如何获取输出电流信息。因为原理图上运放输出编号为Iout，所以有这个疑问。

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Johnsin Tao：

Hi

     过流不就是需要电流采样，达到保护界限就保护。