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TAS5768M: uppaer voltage cutting problem

Part Number: TAS5768M
Other Parts Discussed in Thread: TAS5766M, TAS5756M

When I play ~800 hz sinus test data on TAS5768M (I2S bus used) after some %60 value of the volume, output of the TAS5768M deteriorates

actually voltage over cutted from above and bottom , I used Pure path console and only and register dump to h file then load to the TAS5768

chip, I don't use any EVM for this work, can you help please?

used platform :PPC3 console

ı2s bus 44100 hz ,16 bit data

target voltage 12V

is there any way like AGC (aoutomatic gain control) for solving that problem 

  • Hi, based on your description, the PVDD voltage is 12V, right?

    Is so, when output big power, the output voltage will be limited by PVDD (12V) as your scope curve.

    Here are some options to avoid this PVDD clipping distortion:

    • Increase PVDD to output bigger output power without clipping.
    • Configure PPC3 Smart Amp to decrease the gain and avoid PVDD clipping.

    Regards,
    Matthew

  • Hi Mattew ,

    That doesn't solve my problem,
    if the amplitude of the I2S data increases, it will be owercutted again,
    I2S data 16 bit changes between 0-65535,
    in the example that I posted previous message the maximum amplitude is about 25000(decimal)
    I made the changes that u said , decresed the gain, problem solved the current test file
    but when I give another sinus test signal whose ampiltude 40000, it overcutted again
    I need some setting that :
    when by changing the volume, the output exceeds the 12V, then gain will be decreased automatically,
    the volume will not be able to increase more,
    if output below the 12V, then it can be increased  
    which means AGC (automatic gain control)
    but on this chip I couldn' succeed that issue .
  • Hi Mattew again,

    I searched for my problem a lot,

    I think I need DRC (Dynamic Range Control ) on Pure Path Studio (GDE)

    But I don't have that application,

    I requested one from TI,

    what do you think am I on the right way?

    thanks.
  • TAS5766M/68M is designed to run TI SmartAmp algorithm. You need to first characterize your speaker using a Learning
    Board before you do the fine-tuning in TAS5766M PPC3 GUI. Have you done any of these?

    I would suggest you try TAS5756M instead since you are more familiar with DRC / AGL.
  • I don't have learning board,

    but I entered my speaker's characteristic values and dumped the register.

    The actual problem is about gain control, even if I enter the right speaker parametrics, I think the problem will go on,

    I need to control the gain dynamicallly on the chip according to max RMS values of the input data,

    I think, I need Pure Path Studio GDE for TAS5768M ,

    (www.ti.com/.../aicpurepath_studio

    I requested that application from TI,

    but no answer yet,
  • There is no GDE for TAS5766M/68M. The PPC3 GUI is the only tool that is recommended by TI.
    Is there any TI FAE or Sales that is helping you with your project? I'd like to see how we can help you.

    Andy