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TAS5731M Full Scale DAC output and Gain Control

Andrew Supercharged
Prodigy 180 points


I am trying to calculate the voltage range at the output of this audio amplifier when the input is "100%" (meaning the digital (PCM) audio is at 100%).

So, I'd like to know the full scale output of this device with 0db of gain. Also, where exactly does the gain control take place? Does it happen in the digital domain (in the DAP) or the analog domain?

Thanks!
> Andrew

  • 0
    TI__Guru 57800 points

    Hi, Andrew,

    Welcome to E2E, Thanks for your interest in our products!.

    Basically for the TAS57xx Family, the maximum output voltage comes from the next formula:

    Vo = gain * modulation limit * supply voltage

    Where the gain is controlled by Audio processor, Modulation limit is set with register 0x10 and supply voltage is PVDD. 

    The gain control takes place in the Digital Audio Processing block. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 180 points

    I appreciate the response Diego. So let me make sure I have that right:

    Note: this device will operate in BTL mode.

    If I input a full scale (100% volume) sine wave into this audio amp, and have a gain of 0db, then at the output I will get a sine wave that has a Vpeak of supply_voltage * modulation_limit, correct? Essentially it will be amplifying the signal such that it hits (or nearly hits) the supply rails.

    Also, if I input less than a full scale sine wave (or any other audio), and set a gain of 0db, the signal will be less amplified, correct? It will have a v_peak of approximately 0.5*supply_voltage? So is the output voltage actually the formula below?

    V_out = gain * modulation_limit * supply_voltage * input_amplitude_percentage

    Thanks,

    > Andrew

  • 0 in reply to Andrew Supercharged
    TI__Guru 57800 points

    Hi, Andrew, 

    Your approach is correct, The formula I provided before corresponded to full scale input (100%). 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer