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TAS6424E-Q1: TAS6424E-Q1 Spread Spectrum Issue

?? ?
Prodigy 10 points
Part Number: TAS6424E-Q1
Other Parts Discussed in Thread: TAS6424E,

Tool/software:

(1) Am I correct in understanding that spread-spectrum is enabled not only at 2.1MHz but also at 480KHz and 384KHz PWM frequencies?
(2) Will the calculation formulas also change for 480KHz and 384KHz? Especially the calculation of SS_PRE_DIV.
(3) The SS frequency TYP value of 8% is listed in the performance section, but what is the limit value?

I would like to add to your question,
In (2) below, if the formula remains the same, please tell me what happens to the factor “11” at 2.1MHz at 480KHz.
If the formula remains the same, please tell me how the factor of “11” at 2.1MHz would be at 480KHz.

In (3) below, the 8% deviation range mentioned means that Fmin varies in the range from Fcent to (1-8%) x Fcent with respect to Fcent.
Is it correct to say that Fmin varies in the range from Fcent to (1-8%) x Fcent?

  • +1
    TI__Mastermind 19250 points

    Hi,

    TAS6424E does not support spread spectrum at 384KHz/480KHz Fsw.

    The SSC only can be enabled at 2.1MHz/1.82MHz Fsw. And the datasheet setting best optimized.

    Regards,

    Derek

  • 0 in reply to Yanming Gong
    Prodigy 10 points

    Hello, I found a reply on your web site about whether TAS6424E-Q1 can do frequency spreading at 384 and 480kHz, please ask which one is accurate?

  • 0 in reply to ?? ?
    TI__Mastermind 19250 points

    Hi,

    TAS6424E SSC only can be enabled at 2.1MHz/1.82MHz Fsw.

     

    Regards,

    Derek

  • 0 in reply to Yanming Gong
    Prodigy 10 points

    Hi, from the actual results, we set the spreading frequency at 384 and 480kHz and also measured the frequency after spreading. For example, 0x77 is set to 84 0x78 is set to 20 0x79 is set to 05. Is there any risk, please advise!

  • 0 in reply to ?? ?
    Prodigy 10 points

    Addendum: 0x28 set to EA

  • 0 in reply to ?? ?
    TI__Mastermind 19250 points

    Please check audio performance.

  • 0 in reply to Yanming Gong
    Prodigy 10 points

    Now trying to calculate the deviation of the spreading frequency, I found that following the formula provided in the datasheet gives different results. Which formula should I use?

    The setting is now 0x28 EA 0x77 84 0x78 30 0x79 05. The deviation calculated with the first formula is 6.25%. The second formula calculates 4%.

  • 0 in reply to ?? ?
    Prodigy 10 points

    Additional questions：

    1.As TYP value, frequency variation 8% is requested in datasheet, how about max one?

    2.For example, when setting PWM frequency to 480kHz, and register 0x77 to 84, 0x78 to 30, 0x79 to 05 .

    Make sure which one is correct to calculate the max/cent/min spread-spectrum frequency for keeping variation not over 8% (+/- 4%) spec?   

    1)As per fomula below, we get Fmin=256*48kHz/(48*2+2+4)=120.5kHz

                                                 Fcent=256*48kHz/(48*2+2)=125.4kHz

    So, Fsw_ssΔ=(125.4-120.5)/125.4=3.9%<4%(spec)

        2)As per another below, we will get the bad variation result of  Fsw_ssΔ=4/64=6.25%>4%(spec)

    3., How can we get Fpwm_cent  according to a certain  formula from Fcent？

    1. We found RE performance of 1/2 PWM frequency( 240kHz point) is NG due to 13dB over. How to optimize the parameters for better one?
  • 0 in reply to ?? ?
    TI__Mastermind 19250 points

    Hi,

    As we found, at 480KHz Fsw, SSC enabled will bring audio band noise. So please do not use SSC at 480KHz Fsw.

    What's the EMI problem? If you set 480KHz Fsw and EMI issues on 480KHz or 960KHz/ 1.44MHz, you should tune LC fliter to suppres the fundamental energy.

    Once more: datasheet SSC setting is optimized for 2MHz Fsw. 480KHz Fsw does support SSC.