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TLV320AIC3254EVM-K: Route AGC to headphone output with AIC254 CS

Mihaly Nemeth-Csoka
Prodigy 20 points
Part Number: TLV320AIC3254EVM-K

Tool/software: AIC3254 CS

I'm using the TLV320AIC3254EVM-K with default configuration.

How can I get the AGC example under Features (AGC_ON_BOARD_DIFF_MIC.txt) to be routed to the Headphone Output?

I was able to change the Input from IN3 to IN1 through Audio Inputs menu successfully.
And I also have working Headphone Output in other examples configured with Audio Outputs menu accordingly.

Do I need to use the MixerAmp (MAL/MAR)? Or do I need some kind of MicroDSP-Code to connect ADC with DAC?

  • 0
    TI__Mastermind 46835 points

    Hi,

    Today is a holiday for our team in the U.S. We will follow up with you on Tuesday.

    Thank you for your patience,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    TI__Mastermind 46835 points

    Hi Mihaly,

    You could use the mixer amps to route the PGA output to the headphone outputs.

    You could also use the loopback to route the ADC output directly back into the DAC input

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 20 points

    Hi Jeff,

    I got it both working, thank you.

    What would you recommand for a system with AGC where we want the output to be in the small range of 400mV +-20mV?

    Does the Fine Gain Adjustment just work for the Mixer Amps or do you recommend to use the Loopback?

  • +1 in reply to Mihaly Nemeth-Csoka
    TI__Mastermind 46835 points

    I would choose the mixer amps over the loopback since you would not loose any quality by avoiding the A-D-A conversion. 

    In case you haven't seen it, there is an application note describing in some more detail the features and parameters of the AGC. This can help you set the exact parameters. The EVM GUI also has a nice tool that lets you see the visual of how it is working. https://www.ti.com/lit/an/slaa446/slaa446.pdf?ts=1740172324299&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTLV320AIC3254

    Setting the 400mV level depends on your gain staging for the rest of the codec. The AGC will consider its target level to be the dBFS value of the ADC output with respect to the full scale value. Even though you are using the mixer amps, the AGC controls the PGA with respect to the ADC output so we have to consider the ADC output to get it to work correctly. So for the given set up below, a value of 0.375Vrms would be 0dBFS. This obviously isn't high enough so you'll need to add some extra gain on the DAC side. 

    Assuming you target something like -6dBFS as the AGC target level, you could add an additional 6+dB ( a little extra needed to get from 0.375 to 0.4) to get the output level correct on the DAC side. 

    It's hard for me to recommend exact AGC values since many parameters are at play, but I hope this points you in the right direction and helps you converge on the right settings for you.

    Best regards,
    Jeff McPherson