LM5036: Low frequency ripple issue

Minqi Zhao

Intellectual 1660 points

Part Number: LM5036

Dear expert,

My customer is using LM5036 in telecom power module.

Vin： 36-75V

Vout：12V

Pout：200W

However customer found that output ripple voltage is large and has low frequency component. Please see sheet 1(Vin=36&48V, Io=16A), the lower the Vin is, the low frequency ripple is larger.

Besides, customer tested on EVM( LM5036EVM-294 without any change), please see sheet 2(Vin=36&48V, Io=8A) still find the low frequency component. Could you help to check on your EVM board?

If this low-frequency ripple cannot be effectively suppressed or eliminated, they'd like to know whether there is a corresponding explanation from TI to explain the cause of the problem. So that they can give a reasonable explanation to the end customer. The main concern of the end customer is that their loop compensation is unstable and there is interference on the layout. Thanks for your support.

PRJ0345-0012低频振荡.xlsx

over 5 years ago

0 Teng Feng over 5 years ago

TI__Genius 13660 points

Hi Minqi,

In my view, this voltage ripple is reasonable, except for switch ripple, such as sample error, loop response delay etc will also introduce ripples.

In the provided waveform, the peak-peak ripple is 60mV, I think it is ok if it satisfies the specs requirement.

Regards,

Teng

0 Minqi Zhao over 5 years ago in reply to Teng Feng

TI__Intellectual 1660 points

Hi Feng,

Thanks for your explanation. One more question, is there any method that can suppress the sample error, loop response delay etc can will lead to the low frequency ripple? Thanks.

0 Teng Feng over 5 years ago in reply to Minqi Zhao

TI__Genius 13660 points

Hi Minqi,

I am closing this post now, since it is supported by email. Thank you.

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LM5036: Low frequency ripple issue