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TAA3040: clipping function

Toshiro Imi
Expert 7570 points

Part Number: TAA3040

Hello.

Our customer has a question if TAA3040 build in clipping function when input overflow. 

Since he found out output voltage rollover phenomenon, he is investigating if this phenomenon comes from either TAA3040 or software.

Best regards,

  • 0
    TI__Guru 50540 points

    Hi Imi-san,

    I do not know what you mean by "clipping function." Do you mean anti-clipping? Clipping is not a function of a device. It is a result of either saturation of the analog or digital stage.

    Voltage roll over can happen if the clipping becomes so extreme that it causes the digital two-complement signal to wrap around itself. Sometimes this also happens due to misalignment of the I2S transmitter and receiver. If the customer is experiencing Voltage roll over it is almost certainly a digital issue.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    TI__Expert 7570 points

    Jeff-san,

    "clipping function" that I posted is that the ADC output is saturated in case input analog signal is exceeded the input range, keeping either the output max or min.

    Does TAA3040 work like this ?

    The background of this question is as shown below.

    (Customer comment)
    What I want to check is what the output will behave when the ADC gain reaches to 0 dB with overflow. I also need to know the frequency characteristics.
    Though I am thinking that TAA3040 output clipping, tell me if any other phenomenon will be happened e.g. rollover.
    What about low frequencies (e.g. 50Hz) or slower signal comes in ?
    The reason why I ask this is I can see rollover like waveform by 50Hz high volume audio signal came in to the mic, and need to know the root cause.

    regards,

  • 0 in reply to Toshiro Imi
    TI__Guru 50540 points

    Hi Imi-san,

    Yes the device will clip normally when the ADC signal reaches 0dB. This happens at all frequencies.

    Rollover like this only happens in the digital domain. So if digital volume is still 0dB (only analog gain is changed), then this is caused by a bit misalignment between the receiver and transmitter. However I have not personally seen this happen at only specific frequencies. Is the customer implying that at higher frequencies (1k for example) the rollover does not happen?

    Thank you,
    Jeff McPherson

  • 0
    Prodigy 20 points

    Hi Jeff-san
    thank you for your comments.

    the symptoms we experienced are similar to the waveform show in attached file

    colud this waveform be caused by ADC??ADC items.pptx

  • 0 in reply to Mitsuru Inoue
    TI__Guru 50540 points

    Hi Inoue-san,

    As I mentioned this is most likely a digital issue. I highly recommend you double check your I2S settings on both the receiver and the ADC output to confirm that the format is matching for both. You can also experiment by adding offset to the ADC output to quickly investigate bit misalignments.

    The second item looks like intermittent glitches caused by timing errors. It would be good to double check that your I2S clocks are meeting the timing requirements of the ADC.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    TI__Expert 7570 points

    Hi Jeff,

    Thank you very much for your help.

    Your suggestion resolved our customer issue.

    Best regards,