TPS54332: EMI/EMC Radiation Issue

SUMIT RANJAN

Expert 1985 points

Part Number: TPS54332

Hi Team,

I am using TPS54332 in our design and during certification we found we have radiation from TPS54332. I used RC snubber circuit of different value and checked on multiple option but still no improvement.

Layout is also as per guidelines. When using near field probe near Ic then we have switching frequency noise of 1MHz and lot of harmonics are there.

Please refer below schematic. Let me know how can we take care of this immediately.

over 4 years ago

0 Shawn Nie over 4 years ago

TI__Genius 10070 points

Hi,

Please re-attach the schematic and layout files, I can't see it.

Shawn

0 SUMIT RANJAN over 4 years ago in reply to Shawn Nie

Expert 1985 points

Hi Shawn,

Please find attached schematic in pdf format. and layout in PNG format of both Ic.

U11 & U12 Placement.zip Power Schematic.pdf

0 Shawn Nie over 4 years ago in reply to SUMIT RANJAN

TI__Genius 10070 points

Hi,

The switching noise can't be filtered by RC snubber, you can add input EMI filter to solve this issue.

Shawn

0 Shawn Nie over 4 years ago in reply to SUMIT RANJAN

TI__Genius 10070 points

Hi,

1MHz is the switching frequency, of cause you can see this noise.

Are you considering conducted EMI (150kHz to 30MHz) or radiation EMI (30MHz to 150MHz)?

What is the frequency which is over the EMI limit? How do you locate the issue is related to TPS54332?

Shawn

0 SUMIT RANJAN over 4 years ago in reply to Shawn Nie

Expert 1985 points

This has been observed in both conducted and radiated. Radiation it is more and its getting fail.

Radiation EMI is tested from 30MHZ to 1GHz and I tested with near field probe in house from 31MHz to 61MHz with RC snubber circuit.

I can see easily there is radiation on Switcher IC body and even with multiple RC combination it is still there.

It is getting controlled after adding copper tape (Shield) on Switcher area. Please find attached image of without any modification radiation pattern, with shield radiation pattern.

You can see difference easily.

0 Shawn Nie over 4 years ago in reply to SUMIT RANJAN

TI__Genius 10070 points

Hi,

There is no many methods which can filter the switching frequency, from my experience:

1. use shield inductor

2. optimize the layout, reduce the copper area of SW

3. add a shielding case (you have checked this method)

Shawn

0 SUMIT RANJAN over 4 years ago in reply to Shawn Nie

Expert 1985 points

Hi Shawn,

Thanks for update. Just for information, in our design we are already using Shielded inductor. I never seen this much radiation from buck converter body itself in my past experience.

This is my first time when i have seen this.

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TPS54332: EMI/EMC Radiation Issue