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TLV320AIC3268: Input Common mode setting

Steven Weng1
Expert 2200 points
Part Number: TLV320AIC3268

Hi TI,

There is an analog source(Line in) and HDMI audio in(via I2S in) on our board. The analog input schematic and input routing are as below.

(1) The blue line is for line input source.

(2) The red line is always routed because the HDMI audio in will be muted if no input selected. so keep IN4L/R routed.

(3) Common mode is used. CM1 for IN1L/R, CM2 for IN4L/R.

(4) Input common mode control(B0_P1_R58): 0xff,   Connected to Internal Common Mode When Not Connected to PGAs

(5) Line in mute control by IN1L/R to PGAs: P1_R52_D[7:6], P1_R55_D[7:6] and CM1 common mode setting: P1_R54_D[7:6], P1_R57_D[7:6]

When mute line in, set P1_R52_D[7:6], P1_R55_D[7:6], P1_R54_D[7:6], P1_R57_D[7:6] to not routed. The line in audio is not muted completely...

After setting input common mode(B0_P1_R58) to 0x00.  The mute function is OK. Why?

Does the "Input commn mode control"  is used for?

Thanks.

BR,

Steven

  • +1
    TI__Expert 6440 points

    B0_P1_R58 settings weakly connect the input pins to the device's common mode. It is used to reduce pop when powering up the ADC path. It is not required.

    Best Regards.

  • 0 in reply to Diljith
    Expert 2200 points

    Hi Diljith,

    Thank for your reply.

    There is a pop noise while line input source signal with about 0.5Vrms but not routed to PGAs in our another board.

    Set B0_P1_R58  connect the input to common mode that solve the pop issue in our another board.

    That two board used the similar audio circuit(use aic3268 both) but have a different result.

    This is a hardware issue?

    Best regards,

    Steven

  • +1 in reply to Steven Weng1
    TI__Expert 6440 points

    B0_P1_R58 is a feature provided to solve such issues. You can try it and see if it resolves the issue on the other board.

    Let me know if you face any issues in resolving the pop.