Power ManagementのトピックRe: MC35FS6513CAE pi filter value requriement

MC35FS6513CAE pi filter value requriement

qiaoqin_wang — Wed, 06 Jul 2022 12:25:45 GMT

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.

Re: MC35FS6513CAE pi filter value requriement

guoweisun — Thu, 07 Jul 2022 06:09:43 GMT

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

Re: MC35FS6513CAE pi filter value requriement

qiaoqin_wang — Mon, 11 Jul 2022 01:30:14 GMT

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.

Re: MC35FS6513CAE pi filter value requriement

guoweisun — Mon, 11 Jul 2022 04:18:12 GMT

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

Re: MC35FS6513CAE pi filter value requriement

qiaoqin_wang — Tue, 12 Jul 2022 02:02:06 GMT

hi guo

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

Re: MC35FS6513CAE pi filter value requriement

guoweisun — Tue, 12 Jul 2022 05:03:19 GMT

从波形上看这个是Vsup跳变从10V 跳到了30V，是这样吗？

Re: MC35FS6513CAE pi filter value requriement

guoweisun — Tue, 12 Jul 2022 05:17:55 GMT

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

Re: MC35FS6513CAE pi filter value requriement

qiaoqin_wang — Tue, 12 Jul 2022 07:08:22 GMT

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。

Re: MC35FS6513CAE pi filter value requriement

guoweisun — Tue, 12 Jul 2022 07:36:14 GMT

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

Re: MC35FS6513CAE pi filter value requriement

qiaoqin_wang — Tue, 15 Nov 2022 10:14:29 GMT

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；

-40C的时候波形；

2.85C的测试波形；

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。

Re: MC35FS6513CAE pi filter value requriement

guoweisun — Tue, 15 Nov 2022 11:09:34 GMT

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。

Re: MC35FS6513CAE pi filter value requriement

guoweisun — Tue, 15 Nov 2022 11:18:56 GMT

Search | NXP Semiconductors

下载这个AN5238上面有硬件的设计。