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LM48580: 48580 will bring relatively large ripple to the power supply,

aiwen chen
Intellectual 625 points
Part Number: LM48580

We are using an LM48580 to drive a piezoelectric speaker, measuring the power supply pin of 48580, 48580 will bring relatively large ripple to the power supply, the peak value is about 900mv, there is no problem without a buzzer, with a buzzer there will be a large ripple problem，please  help check  it  ，What is the problem？

  • 0
    TI__Guru** 109165 points

    Hi Aiwen,

    Can you share the spec of the speaker being used? Also what is the current rating of R47?
    You may need to increase the decoupling capacitors close to the device. You can increase the capacitance value of the VDD decoupling, and also increase the voltage rating of the VBST decoupling.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Intellectual 625 points

    BPR2207H0.65-F2规格书(A0)(1).pdf

    this  is  our Piezoelectric speakers Part number BPR2207H0-F2，I use a lithium battery to power the evaluation board 48580 and then add an audio signal to the 48580 signal input. The piezoelectric speaker is connected directly to the output of the EV kit 48580. The oscilloscope now measures the power supply (VDD) of the evaluation board (the output interface of the lithium battery), The measurement results still have a large amount of power supply ripple。

  • 0 in reply to aiwen chen
    TI__Guru** 109165 points

    Hi Aiwen,

    Just to compare, can you also share the results using a bench power supply?
    Is this ripple causing artifacts at the output? Or is this just a power related concern? You may try by increasing the value of the series resistor to reduce the current peaks from the capacitive load.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Intellectual 625 points

    If it is a series resistor, where should it be in series?

  • 0 in reply to aiwen chen
    TI__Guru** 109165 points

    Hi Aiwen,

    I mean in series with the speaker load, connected to the output of LM48580. Based on the schematic you shared, there is already a series resistor R47, you can replace this resistor with a larger value.

    Best regards,
    -Ivan Salazar
    Applications Engineer