LM5017: Reduce the FB ripple

Gene Qiu

Part Number: LM5017

Hi team

when using LM5017 as below circuit, i found the FB pin ripple has a big spike during ON time pulse. Is there any method to reduce such spike?

the fsw is around 380kHz, the output capicitor is ceramic Capacitor 10uF with around 20-30 mohm.

over 4 years ago

0 J Arrigo over 4 years ago

TI__Mastermind 28020 points

Hi Gene,

Lower value ceramic capacitors are effective at reducing high frequency ripple. Try placing an additional 1uF and 100nF capacitor at the output.

Also, when measuring the ripple voltage, make sure to use a very short, close-coupled ground for your probe. The inductance of a long scope ground wire will show up as high frequency noise.

Regards, Jason

0 Gene Qiu over 4 years ago in reply to J Arrigo

TI__Intellectual 1720 points

Hi Jason

Regarding ''Try placing an additional 1uF and 100nF capacitor at the output'', customer already put 10nF and two 4.7uF afterwards. Is it enough?

Best Regards

Gene

0 J Arrigo over 4 years ago in reply to Gene Qiu

TI__Mastermind 28020 points

Hi Gene,

The capacitors placed could be enough. I'm not sure of the placement of these caps. Have them try measuring the ripple across the capacitors using a tight, close-coupled ground lead of the scope.

Regards, Jason

0 J Arrigo over 4 years ago in reply to J Arrigo

TI__Mastermind 28020 points

Hi Gene,

I haven't heard back in a while. Hope that means this issue is resolved.

I will close this post. You can respond and re-open the post if needed.

Regards, Jason

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LM5017: Reduce the FB ripple