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TLV320AIC33: PGA bypass path with AGC

Steven Weng1
Expert 2200 points
Part Number: TLV320AIC33

Hi Tis,

Please help check.

I have tried the AGC function on I2S record path and it works well.

But the AGC function have no effect on PGA bypass path. is it right?

Sorry! another question about the AGC max gain(Page 0, Reg 27, Reg 30)

I tried to measure the background noise floor on our environment. Just increase the max gain then measure the level of I2S record file as below(noise gate is disabled):

Max gain(dB) Level(dBFS)
0 -44
5 -39
7 -41
9 -39
11 -37
14 -38
17 -35
20 -37
22.5 -35
25.5 -37
30.5 -38
40 -34
50 -24

The level value is strange! Why not increase linearly after the max gain increase?

Thanks!

BR,

Steven

  • 0
    TI__Expert 6440 points

    Hi Steven, 

    The AGC circuit changes the signal gain using the PGA and therefore bypassing the PGA would impact the AGC behavior.

    The MAX GAIN changes is expected to result in a linearly increase the output dB RMS level for low level signals. The output level in the table does not look proper. What was your setup for these tests? It would be good if you can do the measurements using an Audio Precision.

    Best Regards.

  • 0 in reply to Diljith
    Expert 2200 points

    Hi Diljith,

    Thanks for your help.

    I have tried in the bypass path that the PGA automatically adjusts by AGC as you said but the noise gate function is not working!

    The level in the table is measured by audacity: Adjust max gain then record a wav file. check wav file in audacity. I will check the audio settings in record path again.

    Thanks.