LM5176: LM5176 EMI radiation issue

Hsu cheng

Expert 1565 points

Part Number: LM5176

My customer test LM5176 EMI radiation,over 80db at 40~80MHz,Please provide solution,thanks.

over 6 years ago

0 Garrett Roecker over 6 years ago

TI__Mastermind 21720 points

Hi Hsu,

Thanks for reaching out with your question.

Optimizing a design to pass EMC standards can be tough. To help with figure out what might be causing the issue can you please provide, the schematic, layout and EMI report?

Thanks,

Garrett

0 Youhao Xi over 6 years ago in reply to Garrett Roecker

TI__Guru* 78370 points

Hi Hsu,

Any updates on this? As Garrett said, we would like to review the sch, layout and the EMI report before we cab offer some effective suggestions. If you would like to try, you may increase the gate resistor slightly to see any improvement. The 40-80MHz is more related to high di/dt and dv/dt and reducing the FET switching speed can help. If you have no further questions, let us close this thread now, and you can reopen it by following a new post.

Thanks,
Youhao Xi, Applications Engineering

0 Hsu cheng over 6 years ago in reply to Youhao Xi

Expert 1565 points

Customer EMI report is as follows

0 Hsu cheng over 6 years ago in reply to Youhao Xi

Expert 1565 points

Customer lines and layout are as follows:0215-A1A-SCH.pdf 0215-A1B-SCH.pdf 0215-layout.pdf

0 Hsu cheng over 6 years ago in reply to Hsu cheng

Expert 1565 points

Is there any update?

0 Garrett Roecker over 6 years ago in reply to Hsu cheng

TI__Mastermind 21720 points

Hi Hsu,

The engineer supporting this device is currently out of the office an will return Tuesday.

Thanks

Garrett

0 Kai Hsiao over 6 years ago in reply to Garrett Roecker

Guru 12675 points

Hi Sir

May I have any good news for this case ?

Below is LT8390's EMI test report ,For you reference

https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/dc2457af.pdf

0 Youhao Xi over 6 years ago in reply to Kai Hsiao

TI__Guru* 78370 points

Can you try to increase the gate resistor and see if the peak emission at 50 MHz reduced?

Thanks,
Youhao

0 Hsu cheng over 6 years ago in reply to Youhao Xi

Expert 1565 points

The resistance has been tested up to 20 ohms. Of course, the input wattage has increased, but the best case for changing the different values is only 2 ~ 3 db.Is there any other countermeasure?

0 Youhao Xi over 6 years ago in reply to Hsu cheng

TI__Guru* 78370 points

Can I bother you to reduce these gate resistors to 1 or 2 Ohms? I would like to see what is the effects of the gate resistors on your emission.

Thanks,
Youhao

0 Youhao Xi over 6 years ago in reply to Youhao Xi

TI__Guru* 78370 points

Can we assume the issue is resolved? You can always reopen this thread by following a new post.

Thanks,
Youhao

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LM5176: LM5176 EMI radiation issue