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Original question:

TAS6424E-Q1: TAS6424E-Q1 Spread Spectrum Issue

TAS6424E-Q1: TAS6424Q SUPPORT 1ohm 80W IN PBTL MODE& SPREAD SPECTRUM 8% RANGE

user5184363
Prodigy 220 points
Part Number: TAS6424E-Q1

Tool/software:

1 .Does it support 1ohm 80W  in PBTL mode,and if there is some potential risk about other specification？

2. Spread spectrum 8%　is　PWM ±8%　or±4%？

  • 0
    TI__Mastermind 36695 points

    Hi,

    1. 80W into 1 ohm in PBTL is possible.  Driving a 1 ohm speaker is a challenge.  The current is high and you will need good speaker wires.  You will be close to the current limit and may not meet 80W
    2. ±4% using the values in the datasheet.

    Regards,
    Gregg Scott

  • 0 in reply to Gregg Scott
    Prodigy 220 points

    Thank U,now we use it at　PWM=384k±8% for EMC,but it also can work well and the performance is al ok

  • 0 in reply to Gregg Scott
    Prodigy 220 points

    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 .

    SO we get the

     SS-AMPL=4

    SS-PRE-DIV=48

    SS-STEP=5

     

    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)

     

    The follow blue word is the datasheet content

    • SS_PRE_DIV = (256 * FS / Fcemter) - 2) / 2
    • SS_AMP = 64 * (Fcenter - Fmin) / Fcenter
    • SS_STEP = 16 * 4 * SS_AMP * FSS / Fcenter

     

    The follow equations calculate the output PWM frequency variation with the settings listed previously.

    • Fmin = 256 * FS / ((SS_PRE_DIV * 2 + 2) + SS_AMPL = 256 * 48 kHz / ((31 * 2 + 2) + 2) = 186.18 kHz
    • Fmax = 256 * FS / ((SS_PRE_DIV * 2 + 2) + SS_AMPL = 256 * 48 kHz / ((31 * 2 + 2) - 2) = 198.19 kHz
    • FPWM_min = Fmin * 11 = 186.18 kHz * 11 = 2.048 MHz
    • FPWM_max = Fmax * 11 = 198.19 kHz * 11 = 2.189 MHz

     

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

    • SS_AMP = 64 * (Fcenter - Fmin) / Fcenter

     

    3., How can we get Fpwm_cent  according to a certain  formula from Fcent？ Fcenter*?=480k,the ? is fixed or regulated for 480k

     

    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 Gregg Scott
    Prodigy 220 points

    We found the best set is 0x77 : 84       0x78: 20      0x79:  05,the EMC will be OK, we can not sure about the  spread spectrum is OK or not? and what should to check the other things to make sure we can use the parameter.  PWM=384K and  480K two conditions both use the same parameter

  • 0 in reply to user5184363
    TI__Mastermind 36695 points

    Hi,

    There is another thread from the same IP address on this issue:

    (+) TAS6424E-Q1: TAS6424E-Q1 Spread Spectrum Issue - Audio forum - Audio - TI E2E support forums

    I will close this one.

    Regards,
    Gregg Scott

  • 0 in reply to Gregg Scott
    Prodigy 220 points

    I am so sorry that i found my workmate had asked the same question...   But i think your answer is very professional that i want get your answer,thank U