LM3410: EMI issues with LM3410XSD/NOPB using as backlight driver with 16V@360mA output

Janis Sarikas

Part Number: LM3410

Hello,

We try to use the LM3410XSD as backlight driver with an output of 16V@360mA. Our Prototype is working fine but we have some EMI issues in the range of 240-290 MHz. Even if we pass the quasi-peak measurement in this range we are a little bit afraid that it was just luck for this time.

Here are the results of the EMC laboratory

Picture 1: Antenna - Horizontal

Picture 2: Antenna - Vertical

Picture 3: Quasi-Peak Table

We think that the source is the backlight converter because of some remeasurements using a spectrum analyzer and a near field probe.

Picture 4: Remeasurement - Measurement Point

Picture 5: Remeasurement - Results - Backlight on

Picture 6: Remeasurement - Results - Backlight off

Here is a picture of our schematic.

Picture 7: Schematic of backlight convertion

Do you have any hints how we could improve the results?

Best regards

Janis

over 3 years ago

0 Tuan Tran74 over 3 years ago

TI__Mastermind 18890 points

Hi Janis,

At that high frequencies you can be many things. You can try adding a small capacitor like 1000pF - 0.01uF to ground on the output with C1105 and inductor input to the inductor. This will help with the higher frequencies filtering. The other thing you can try is to add an RC snubber to the switch node to slow down the switching edges. That's all I have to comment on this.

Thanks Tuan

0 Janis Sarikas over 3 years ago in reply to Tuan Tran74

Prodigy 175 points

Hello Tuan,

Thanks for your comments. I will try them out. Especially the RC-snubber sounds interesting.

Best regards

Janis

0 Tuan Tran74 over 3 years ago in reply to Janis Sarikas

TI__Mastermind 18890 points

Hello Janis,

We will close this thread for now and you can reply to it if you have more questions.

Thanks Tuan

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LM3410: EMI issues with LM3410XSD/NOPB using as backlight driver with 16V@360mA output