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Tas3308 + TAS5631 some "ploc" in start-up sequence

guillaume Riviere
Prodigy 140 points
Other Parts Discussed in Thread: TAS5631, TAS3308, TAS5613, TAS5086Hello I currently test a personal board who involve a tas3308 DSP for audio processing together with a tas5613 as power amplifier in a 2.1 configuration, actually everithing work fine expect the power up sequence where a "ploc" could be hear. I tried different start up scheme: - enable TAS3308 - Set TAS3308 parameter and enable PWM - Enable TAS5631 or - Enable TAS5631 - enable TAS3308 - Set TAS3308 parameter and enable PWM in both case i had a "ploc" So did i do the correct start up sequence ?, or did they have some prameter to set on the tas3308 to solve this problem ? Thank's Best regard
  • 0
    TI__Guru**** 189399 points

    Hi, Guillaume,

    I don't support the TAS3308 (I'm on the TAS5631 side of the house), but you need some kind of mode to slowly ramp up the PWM outputs from the 3308. The problem is, the outputs need to be biased at half your power supply in SE configuration, and how you get from zero to that voltage is all about pop.... We also have some split-cap configurations, but again, if there is any difference in voltage on the two sides of the speaker, a pop will occur. Pop is tough to get rid of in SE mode...

    Take a look at the TAS5086 d/s. We have an extra output on that bad boy to drive the split-cap for SE mode. I don't think TAS3308 has this feature...

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 140 points

    Hi Don

    I take a closer look on the TAS3308 documentation, apparently the chip have a start-up procedure who handle SE configuration.

    But i'm not sure if TAS5631 is compatible with it, could you confirm ?

    " The TAS3308 provides an soft start initialization sequence that charges the split capacitor through the
    loudspeaker. In order to do this without audible artifacts the charge current is limited by applying a start
    sequence which charges the output state between low, high and high-Z. Because the output stage is in high-Z in
    a part of the sequence, the resulting output impedance can be brought to a level suitable for charging the split
    capacitors without audible artifacts. This solution does not require external components, as shown in Figure 5.5.
    Not all power stages are compatible with the mid-Z scheme. Please refer to the power-stage data sheet for
    compatibility. 
     
    To support single ended operation the TAS3308 has a soft start circuit which charges the split capacitor. This is
    controlled by the PWM Duty 50 Mode Control register (0x1D). "

     

    Thank's

    Best regard