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LM49352: lm49352 Class D amplifier LS+/LS- waveform and failure issue.

Prodigy 160 points

Replies: 16

Views: 632

Part Number: LM49352

Hi,

As mentioned on datasheet, LS+ and LS- should have a 300KHz waveform after power on. But I get a 450KHz waveform as measured. Please explain how and why the frequency of the waveform is affected?

The speaker has voice for couple minutes even the frequency is 450KHz, but the waveform is gone forever after a few minutes. And it can't be recovered by cut off power. It seems class D amplifier is broken. Can you also explain this?

Thanks,

Roger Luo

  • Roger,

    can you send me your LM49352 register configuration?

    As far as I know there is no way to control the CLASS-D amplifier modulation frequency, and it should not be 450kHz.

    best regards,
    -STeve Wilson
  • In reply to Steve-Wilson:

    Hi Steven,

    The register cofiguration is as below:

    (0x00, 0xa9)
    (0x01, 0x01)
    (0x02, 0x01)
    (0x1b, 0x00)
    (0x20, 0x12)
    (0x21, 0x00)
    (0x30, 0x11)
    (0x31, 0x00)
    (0x40, 0x0f)
    (0x41, 0x01)
    (0x44, 0x09)
    (0x50, 0x2f)
    (0x10, 0x03)
    (0x14, 0x80)
    (0x23, 0x1f)
    (0x42, 0x05)
    (0x89, 0x64)
    (0x8a, 0x33)
    (0x81, 0xf0)
    (0x82, 0x1f)
    (0x83, 0x1f)
    (0xa0, 0x10)
    (0xa1, 0x1f)
    (0xa2, 0x00)
    (0xa8, 0x70)
    (0xa9, 0x33)
    (0x15, 0x0c)
    (0x16, 0x08)
    (0x54, 0x00)
    (0x55, 0x00)
    (0x56, 0x00)
    (0x70, 0x0e)
    (0x71, 0x07)
  • In reply to Roger Luo:

    Hi Steven,

    As long as I set four registers below, LS+ and LS- have waveform output and the frequency is always 450KHz.

    (0x00, 0xa9)
    (0x01, 0x01)
    (0x02, 0x01)
    (0x10, 0x03)

    Please help to find the cause. Is there any side-affect if class D is working on 450KHz?

    Thanks,
    Roger Luo
  • In reply to Roger Luo:

  • In reply to Steve-Wilson:

    Hi Steven,

    Any comments on this? The volume of speaker is also low. I set the registers 0x14, 0x40, 0xa8 and 0xa9 to maximum value but the volume is still low. Is this related to the frequency of square wave?

    Thanks,

    Roger Luo

  • In reply to Roger Luo:

    Roger,

    if you change reg 0x01 value to 0x02, do you see any change?

    best regards,

    Steve Wilson

  • In reply to Steve-Wilson:

    Hi Steve,

    The frequency of LS+/LS- has no change if I change reg 0x01 value to 0x02. I always get the same frequency 450KHz. And the volume of Speaker is always low even I set the LS amplifier to maximum. Do you think low volume is caused by frequency 450KHz? Are they related?

    Thanks,

    Roger

  • In reply to Roger Luo:

    Roger,

    Do you have a schematic you can share? This is not correct behavior there must be some explanation.
    -Steve Wilson
  • In reply to Steve-Wilson:

  • In reply to Steve-Wilson:

    Hi Steve,

    Please check the schematic posted. I'm looking forward to your reply.

    Thanks,
    Roger

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