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TPA3128D2: Question for gain adjustment, THD+N and Sync pin

Kazuki Kuramochi
Genius 10585 points
Part Number: TPA3128D2

Hello expert,

I have several questions for TPA3128D2.

First, could you provide TPA3128D2 gain setting formula regarding R1 and R2? Because datasheet is only explained about the gain setting under 20dB, 26dB, 32dB and 36dB. But my customer would like to adjust the gain more precisely(e.g. 23db).

Next, Would you explain about why datasheet has the THD+N characteristic under 6kHz? I guess this situation will tend to cause the worse THD+N performance due to this devices design. So you indicated the THD+N performance under 6kHz.

Last, How many TPA3128D2's Sync Pin could we connect in parallel? This point is not on datasheet and typical application is only using 2pcs TPA3128D2. So we'd like to know about the maximum value of sync pin connection in parallel.

I'm looking forward to hearing back from you.

Best regards,
Kazuki Kuramochi

  • 0
    TI__Expert 6720 points

    Hi Kuramochi-san,

    1. TPA3128D2 only has four gain settings internally, and it is configured through different R1/R2 setting. So it's not possible to set gain as customized value, such as 23dB.
    2. It's not quiet sure about your question. My understanding is why datasheet shows 6kHz THD performance, and the reason is to show worst high frequency THD with 20kHz AP filter setting.
    3. Also not clear about Sync pins. Do you mean which pin can be tied together when using 2pcs TPA3128D2?

    Regards,

    Matthew

  • 0 in reply to Matthew Miao
    TI__Genius 10585 points

    Hi Matthew-san,

    I appreciate your prompt support.

    1. I understand TPA3128D2 cannot configure the gain as which is not on datasheet.
    2. I get it about 6kHz THD+N performance is worst under 20kHz AP filter with TPA3128D2.
    3. TPA3128D2 has SYNC pin(pin16) for synchronizing multiple TPA3128D2's operation. Customer think about using 3 or more TPA3128D2 on the same board. So they would like to know how many devices could be connected to SYNC pin.

    Best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Expert 6720 points

    Hi Kuramochi-san,

    As for pin 16 SYNC, how many devices in customer system? Based on my understanding, only one Master device with several Slaver devices should work, and the reference circuit can be found with datasheet '8.2 Typical Application' section.

    Regards,

    Matthew

  • 0 in reply to Matthew Miao
    TI__Genius 10585 points

    Hi Matthew-san,

    Sorry for my rate reply.

    Customer still is in advanced development stage and they don't have detailed quantity of devices. So they ask me about the quantity of maximum connection devices on Sync pin.

    Best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Expert 6720 points

    Hi Kuramochi-san,

    Design team confirmed that there is no specific Slaver device limitation as long as SYNC pin can drive parasitic cap.

    So normally it's no issue with real speaker system.

    Regards,

    Matthew

  • 0 in reply to Matthew Miao
    TI__Genius 10585 points

    Hi Matthew-san,

    Thank you for your prompt confirmation.

    I understand about that we don't have detailed information regarding this but it probably can connect multiple device on SYNC pin.

    Best Regards,
    Kazuki Kuramochi