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LP5569: PWM noise work around

Kazuki Kuramochi
Genius 9040 points
Part Number: LP5569

Hello expert, 

I have question for counter measure of PWM switching noise from LP5569.
In previous discussion on E2E, I have been suggested to add cap between Outx(LEDx) and GND.

However, LP5569 is current sink device and our use case is that all power for LED is from internal boost converter.
Then, I think we should add cap between Vout and GND.

Is this my understanding correct?


Best regards,
Kazuki Kuramochi

  • 0
    TI__Genius 9040 points

    Hello Expert,

    Sorry for sending at once.
    After first post, I realized some option to connect cap between OUT(VOUT or LEDx) as follows.


    Which pattern is best from the point of view of noise?

    Best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Expert 7865 points

    Hi Kazuki,

    Sorry for my late replay.

    a 1uF cap is suggested to connected between VOUT and PGND pin for reduce the noise of Vout. The voltage of LED is from internal charge pump. And pattern (2) as you shows is best to reduce the noise from long trace for LED line. The value of cap is determined by your actual circuit.

    Best Regards

    Monet Xu