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TAS2770: when I increase the PCM volume above -20dB, TAS2770 shuts the PWM off

Ellab Yoon
Prodigy 10 points
Part Number: TAS2770
  • the speaker is rated for 3W and its impedance is 8ohm.
  • with a 12V VBAT.
  • the DVC_PCM is set to -30 dB
  • the amplifier level to 21dBV.

The issue is when I increase the PCM volume above -20dB, TAS2770 shuts the PWM off. It does not recover until the board is rebooted, even if the volume is lowered.

Please help me to solve this issue.

  • 0
    TI__Genius 16930 points

    Hi Ellab,

    Is this happening on a TI EVM or a different PCB?
    does this occur with no speaker attached to device? Does this occur when using a different speaker?

    This sounds like it may be a over current event happening on the output of the amplifier. this can be verified. if you read book 0 page 0 register 0x24 a value of 0x02 would indicate an over current event happening.

    if this is happening the device is likely being put into SW shutdown. can you read book 0 page 0 register 0x02 after this error happens to verify this?

    Regards,

    Arthur Brown

  • +1 in reply to Arthur Brown
    Prodigy 10 points

    Hi Arthur,

    Thanks you for the feedback.

    • it's happening on a our PCB(based on i.MX8M Mini)
    • register values while working fine: 0x02=0x0c, 0x05=0x3d, 0x24=0x04
    • register values when it's stopped: 0x02=0x0c, 0x05=0x15, 0x24=0x00

    http://cube.geek.perl.sh/ti/codec/tas2770_schem.png

    fine bad
    00: 00 00
    01: 00 00
    02: 0c 0c
    03: 14 14
    04: 01 01
    05: 3d 15 << playback volume for PCM
    06: 00 00
    07: 07 07
    08: 00 00
    09: 08 08
    0a: 07 07
    0b: 02 02
    0c: 02 02
    0d: 10 10
    0e: 13 13
    0f: 02 02
    10: 00 00
    11: 04 04
    12: 06 06
    13: 07 07
    14: 08 08
    15: 14 14
    16: 76 76
    17: 10 10
    18: 6e 6e
    19: 1e 1e
    1a: 58 58
    1b: 01 01
    1c: 14 14
    1d: 4e 4e
    1e: 00 00
    1f: 00 00
    20: fe fe
    21: b1 b1
    22: 00 00
    23: 00 00
    24: 04 00 << INT_LTCH0: Latched interrupt readback.
    25: 00 00
    26: db db
    27: b8 00 << MSBs of SAR ADC VBAT conversion.
    28: c0 00 << LSBs of SAR ADC VBAT conversion.
    29: 8f 00 << SARD ADC Temp conversion.
    2a: 40 00 << SARD ADC Temp conversion.
    2b: d1 d1
    2c: c0 c0
    2d: ae ae
    2e: a0 a0
    2f: 02 02
    30: 05 05
    31: 00 00
    32: 81 81
    33: c0 c0
    34: 00 00
    ...
    3b: 00 00
    3c: 0c 0c
    3d: 03 03
    3e: 2c 2c
    3f: 00 00
    40: 00 00
    41: 00 00
    42: 30 30
    43: 00 00
    ...
    72: 00 00
    73: ff ff
    74: 00 00
    75: ff ff
    76: 00 00
    77: 7f 7f
    78: 00 00
    ...
    7c: 00 00
    7d: 10 10
    7e: 8b 8b
    7f: 00 00
    80: 00 00

    Best,
    Ellab

  • 0 in reply to Ellab Yoon
    TI__Genius 16930 points

    Hi Ellab,

    there is no obvious issue with the registers you shared.

    I will try to replicate this issue on hardware here, and get back to you. If this issue does not happen on the EVM then I suspect a board layout issue.

    can you please share the layout of your design? as well as the BOM

    thank you and regards,

    Arthur Brown

  • 0 in reply to Ellab Yoon
    Prodigy 10 points

    I'm sorry.
    It's not resolved.
    I accidentally pressed the green button.
    Is there any way to get it back?

  • 0 in reply to Ellab Yoon
    TI__Genius 16930 points

    Ellab,

    Don't worry, we will not close the thread until this is resolved.

    I do have one question, what input are you giving to the device? is it playing music or a pure tone?

    if you increase the DVC_PCM volume above -20 with no input does the PWM shut off?

    Regards,

    Arthur Brown

  • 0 in reply to Arthur Brown
    TI__Genius 16930 points

    What speaker impedance are you using?

  • 0 in reply to Arthur Brown
    Prodigy 10 points

    Arthur,

    I'm playing a 1kHz tone and some music.

    There's no PWM signal while I2S is stopped.
    so I can't know the state of the output port.
    How can I tell if the PWM has shut off when I'm not playing anything?

    Best,
    Ellab
                                                                                                                                                                                                                                                                                                                                                                                                                                           

  • 0 in reply to Arthur Brown
    Prodigy 10 points

    8 Ohm and 4 Ohm speakers

  • 0 in reply to Ellab Yoon
    TI__Genius 16930 points

    Hello Ellab,

    I am very sorry for the delay.

    The PWM should be visable on an O-scope when TAS2770 is in active mode even with no output playing.

    I looked over your schematic and have one suggestion. the VSNS pins should be connected across the speaker after the filter. Can you short the inductors and remove the capacitor, and see if this issue is still present?

    I also assume that this issue happens on all of your boards?

    your schematic otherwise looks correct, and if the issue persists can we connect over email so our team can review your layout?

    Again, sorry for the delay,

    Arthur Brown

  • 0 in reply to Ellab Yoon
    TI__Guru* 95355 points

    Hi Ellab,

    It has been some time since last communication, I'm marking this thread as closed but if you have any further questions please reply or start a new thread.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators