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TLV320ADC6120: How to get a channel gain an AGC unit sets?

Alex Blackberry
Prodigy 10 points
Part Number: TLV320ADC6120

Hi TI experts. I am using TLV320ADC6120 in a modem for a digital information transmission in an acoustic channel. AGC unit in TLV320ADC6120 is enabled. I see in my software that AGC works well and I understand its parameters. The only question that arises is an access to a channel gain the AGC sets. Value CH1_GAIN in register CH1_CFG1 Register (Address = 0x3D) is not changing at all when I am moving a microphone. How can I get a valid channel gaint the AGC sets? I need it to estimate a signal strength in an acoustic channel. Thanks.

  • 0
    TI__Mastermind 23135 points

    Hi Alex,

    Today is a TI US holiday. Our team will get back to you on Tuesday.

    Thank you for your patience,
    Jeff McPherson

  • 0
    TI__Expert 4895 points

    Hello Alex,

    Thank you for bringing this to our attention. Allow me till tomorrow give you a response to this issue. 

    Regards,

    Ore.

  • 0
    TI__Expert 4895 points

    Hello Alex, 

    I would like to understand what you mean by moving the microphone ?

  • 0 in reply to Ore Ogundana
    Prodigy 10 points

    Hi Ore,

    Excuse me for a delay. I have a wireless acoustic communication system that consists of a digital transmitter connected to a loudspeaker and a digital receiver connected to a microphone. I move the microphone to vary a signal pressure level at its input and I see in my programm that a signal level at ADC output is relatively stable. I interpret it as an AGC system in LV320ADC6120 works fine but I can not get a channel gain the AGC sets from TLV320ADC6120's registers. It is the only problem I have with the AGC system.

  • 0 in reply to Alex Blackberry
    TI__Expert 4895 points

    Understood. If I am understanding this right, you are varying the signal pressure level of the mic to the ADC input while the AGC is enabled and you would like to observe and possibly control the gain the AGC creates in this set up? 

    Regards,

    Ore

  • 0 in reply to Ore Ogundana
    Prodigy 10 points

    Yes, it is. Initially I have thought that registers CH1_CFG1 (0x3D) and CH2_CFG1 (0x42) contain the channel gain the AGC system sets but they do not. Contents of these registers is static. Thanks.

  • 0 in reply to Alex Blackberry
    TI__Expert 4895 points

    Hey Alex, 

    I am looking into this issue with our TI expert. Ill give you an update by end of week.

    Regards,

    Ore

  • +1 in reply to Ore Ogundana
    TI__Expert 4895 points

    Hey Alex,

    When AGC is enabled, the channel gain changes in real time based on the signal level and there is no direct access to it. To better help you, what would you like to do while observing the AGC gain? Tell us more about your application and how this step is important in your application. 

    Regards,

    Ore. 

  • 0 in reply to Ore Ogundana
    Prodigy 10 points

    Hi Ore,

    Thank you very much for this valuable information. It has resolved my issue.

    Channel gain is used in receiver DSP algorithms of our modem. It helps to estimate a signal quality because the higher is gain the lower is the signal quality in common. Fortunately we have an AGC system of our own in the modem. Tests showed that it works quite good in connection with TLV320ADC6120. Initially we wanted to use AGC system of TLV320ADC6120 because it works as I understand in a full input bandwidth of ADC but our own AGC system can work only in a bandwidth restricted by interpolation filters of TLV320ADC6120.