This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • TI Thinks Resolved

TLV320AIC3268: Analog Input Connection With Resistor Divider Network

Part Number: TLV320AIC3268

Hi Ti,

According to AIC3268 datasheet, the max input level is 0.5Vrms per input. For differential input, it is up to 1Vrms.

If I want to handle the differential signal with +4dBu level (professional line level, comes from audio mixer, microphone preamp...etc).

+4dBu is about 1.228Vrms so the divider network is necessary!

I am new to audio hardware circuit design. Please help me check:

(1) Use the divider network to half the differential input voltage, enlarge the maximum voltage to 2Vrms.

     In Figure 111. Analog Input Connection With Resistor Divider Network of datasheet, R1 || R2 << Req

     Could you suggest me the resistor value R1, R2 of the divider?

(2) Is it any risk for divider to handle +4dBu signal  for long time? The audio quality is OK?

(3) BTW, use the 1 Vrms  as our differential input maximum voltage and limit audio source output(use audio mixer gain control to lower audio etc.) or use the divider up to 2Vrms. which is better?

      I think lower the audio source gain may decrease the SNR in audio mixer and cause the bad quality. Could you give some suggestions?

Thank you!

BR,

Steven

  • Hi, Steven,

    The TLV320AIC3268 is an audio codec targeted for portable applications, so the compatibility with professional line level is not supported directly and signal conditioning is required. The input conditioning can be achieved  with a resistor divider network as mentioned in section 9.2.2.1 of the datasheet, but for the output signal conditioning, an external amplifier/line driver will be required.

    The selection of the resistor network depends on the PGA and Rin settings, I can help recommending the values but will need that information first. The following formulas are used for the R1 and R2 calculation:

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • In reply to Diego Melendez:

    Hi Diego,
    Thank you for reply.
    I could not see the formula. Could you post again?

    Our product focus on video/audio recorder. For analog audio signal, there are stereo line in jack and stereo differential line in XLR on our custom board. We want to support the professional line level in differential input.

    The PGA and Rin settings are used for gain/level control in our design.
    So the value is not a constant value. Could I use the Rin value for level attenuate control? just three levels for adjusting. such as -12dB, -6dB, 0dB. Or I must set it to a constant value in our usage?

    Thanks a lot.
    Best Regards,
    Steven
  • In reply to Steven Weng1:

    Hi, Steven,

    Sorry, I didn't noticed the image was corrupt. Please refer to below:

    If differential configuration is used, you will need only the value of RIN for the calculation of the required attenuation network. You should be able to change the gain without issues with this configuration. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • In reply to Diego Melendez:

    Hi, Diego,
    The image seems still corrupt. The formula that you mentioned is at 9.2.2.1 of datasheet?
    If I choose RIN 20K Ohms for differential input and attenuation factor is 0.5(attenuate to half). What is recommended value of R1 and R2 in voltage divider network?
    Any suggestions will be appreciate.

    Best Regards,
    Steven
  • In reply to Steven Weng1:

    Hi, Steven,

    Sorry for the issues, I don't know why the image is corrupt. Correct, the formulas are the same of section 9.2.2.1. For differential mode inputs, Rin=Req and the gain does not affect the calculation. So, the only consideration for the R1 and R2 selection would be as follows:

    Req=Rin
    R1 || R2 << Req
    R1 || R2 << Rin
    R1 || R2 << 20KΩ

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.