MC35FS6513CAE pi filter value requriement

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MC35FS6513CAE pi filter value requriement

1,049 Views
qiaoqin_wang
Contributor III

Dear  Mr or Mrs

now we find a problem at our product when we use the MC35FS6513CAE,about the MC35FS6513CAE VSUP power supply pi filter circuit, we design as the below picture:

now  the C166 is 100uf ,when the VSUP power rise up to over than 26V,the Vpre down to 2.3V and Vpre_SW down to 0v;

if i change the C166 to 10uf,when the VSUP power rise up to over than 26V,the Vpre is noraml,

so i want to know the reason ,and the L3 and C166 and C165 value requirement;

looks forward your reply ,thanks.

qiaoqin_wang_0-1657109865548.png

qiaoqin_wang_1-1657109887882.png

 

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11 Replies

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guoweisun
NXP TechSupport
NXP TechSupport

You can catch the waveforms of VSUP1/2/3 and VPRE and VPRE_SW when this issue happened.

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1,017 Views
qiaoqin_wang
Contributor III

Dear sun

thanks for your reply so quickly,as the below is the test waveform, could you help me to analysis it ,looks forward your reply.

qiaoqin_wang_2-1657502958073.png

 

 

 

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1,006 Views
guoweisun
NXP TechSupport
NXP TechSupport

Can you also test these same waveforms without solder 100uF cap on Vsup?

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1,014 Views
guoweisun
NXP TechSupport
NXP TechSupport

Do you test these under DEBUG mode? If not please test it in DEBUG mode.

 

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1,011 Views
qiaoqin_wang
Contributor III

hi guo

Whether in debug mode or not, there is a phenomenon of Vpre voltage drop,thanks。

 

 

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1,007 Views
guoweisun
NXP TechSupport
NXP TechSupport

从波形上看这个是Vsup跳变从10V 跳到了30V,是这样吗?

 

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1,003 Views
qiaoqin_wang
Contributor III

hi guo工

是的,所以想问一下是什么原因,能够帮忙分析一下,谢谢。

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1,000 Views
guoweisun
NXP TechSupport
NXP TechSupport

我在 EVB 上也复制不出来这个问题,您能测试去除100uF电容后的波形吗?除了没有100uF电容其他的测试条件跟上面波形的一模一样我们尝试找找差别

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581 Views
qiaoqin_wang
Contributor III

hi guo工

我们尝试将Vsup1&2的电容更改为4.7uf,Vsup3端为100uf电容,VSUP1&2和VSUP3之间的电容为1uh 4020封装的电感,在高温85C和常温25C下测试波形如下,SBC的各个管教输出正常。

但是在低温下会不停复位或者在极端的情况下会将SBC打坏。

测试波形如下:Ch1:Vsup1&2;Ch2:Vsup3;Ch3:Vpre(是Vpre的SW波形),Ch4:current;

  1. -40C的时候波形;

    qiaoqin_wang_2-1668507086260.pngqiaoqin_wang_3-1668507099232.pngqiaoqin_wang_4-1668507110402.png

     

    2.85C的测试波形;

    qiaoqin_wang_5-1668507142340.pngqiaoqin_wang_6-1668507157363.png

     

    想问一下这个是什么原因引起的,设计VSUp1和VSUP3的LC pi型滤波的时候需要注意什么,有什么相关文档对此作出解释吗?因为我找了FS6500的SBC的手册,没有找到任何关于此电感和电容容值的说明,还请帮忙解释一下,谢谢。

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575 Views
guoweisun
NXP TechSupport
NXP TechSupport

Search | NXP Semiconductors

下载这个AN5238上面有硬件的设计。

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576 Views
guoweisun
NXP TechSupport
NXP TechSupport

注意低温下电容会衰减的很厉害特别是电解电容,你可以在低温下看看SBC的输入电压是不是还是正常的在问题存在的情况下。

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