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TAS2780: Codec output volume level

Francisco Pastorini
Prodigy 120 points
Part Number: TAS2780

Tool/software:

Hello TI team,

We’re working with the TAS2780 and using it as a DAC/amp, but we believe we’re not getting the maximum possible output volume.

Current configuration

  • CDS_MODE = 0x00 (Y-Bridge, High-Power on VBAT1S)

  • AMP_LVL = 0x14 (maximum analog gain)

  • DVC_LVL = 0x00 (no digital attenuation)

Observation

  • Measuring at the speaker outputs with an oscilloscope, the maximum voltage we see is approximately VBAT1S. This suggests the Y-Bridge is active, yet the acoustic level still seems lower than expected.

Questions

  1. Are there protection/limiter mechanisms (e.g., thermal, over-current, undervoltage/battery tracking, clip limiter, etc.) that could be engaging and reducing output? Which status/flag registers should we read to confirm?

  2. Are there other registers that can cap output level despite AMP_LVL max and DVC_LVL = 0x00?

  3. Any recommended checklist to verify we’re truly at maximum output?

Thanks in advance!

  • +1
    TI__Mastermind 20685 points

    Hi Francisco,

    CDS_MODE = 0x00 and VBAT1S Mode = 0x0 will enable Y-bridge and allow maximum power from the output.

    AMP_LVL and DVC_LVL as 0x14 and 0x00 respectively is correct for the maximum output power

    I believe this issue is due to the way BOP is enabled inside our device registers

    we have a top-level control to enable and disable the BOP which is disabled by default. Book0 page0 register 0x1d (B0P0R0x1d) bit 1

    However, each of the 4 levels of BOP have a control to enable/disable, and if this enable is set(whch it is by default) i believe it will still have an effect even if the top level control is 'disabled'

    BOP_DIS3 - B0P0R0x23 - bit 4. set this register to 0x10 to disable

    BOP_DIS2 - B0P0R0x28 - bit 4. set this register to 0x10 to disable

    BOP_DIS1 - B0P0R0x2D - bit 4. set this register to 0x10 to disable

    BOP_DIS0 - B0P0R0x32 - bit 4. set this register to 0x10 to disable

    I suspect this is the reason for the limited output. apologies as i did not test this today before providing you the response. hopefully this is a quick test and you can let me know if the issue is resolved. 

    Regards,
    Arthur

  • +1 in reply to Arthur Brown
    TI__Mastermind 20685 points

    Also, you can verify if the BOP is active based on the LIVE interrupt register flags in B0P0R0x48

  • 0 in reply to Arthur Brown
    Prodigy 120 points

    Thank you for your prompt and good answer, Arthur! I think that we are indeed getting the most that we can from the output. 
    Playing around with the EVM, I disabled the BOP as you mentioned and configured everything the same to get the maximum power and we are getting the same output.
    Could you confirm that using the test tone is a good way to get the most power from the TAS2780?

  • +1 in reply to Francisco Pastorini
    TI__Mastermind 20685 points

    Hi Francisco. 

    Since the TAS2780EVM can be identified as a USB audio device. you can play from the windows media player any audio file. 

    itis very typical, yes, to use a sine tone to quantify the peak power. 

    you can use this attached file which is very loud, so be mindful. 

    There are many good free software's which can be used to generate arbitrary signals for testing. 

    Room EQ Wizard, and Audacity are two that we commonly use, and these have alot of information available online. 

    Regards,
    Arthur

  • 0 in reply to Arthur Brown
    Prodigy 120 points

    Thank you very much for your help, Arthur! It has been of great use Smiley