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RE: Setting the TPA2028D1 AGC, Volume and Mute

Zach Vargas
Prodigy 50 points

Other Parts Discussed in Thread: TPA2028D1

Hi,

I am having similar issues to those described by Myke above:

When trying to control the audio volume (loudness) of a speaker connected to TPA2028D1, I hear no perceivable difference on a variety of settings. As suggested above, I have tried adjusting the fixed gain with AGC turned off (Comp Ratio 1:1). I have also tried a variety of other settings including those suggested by Myke in his post on Mar 28, 2013.

Could anyone clarify the results of this discussion. I noticed that the last post mentioned changing the settings for the limiter and compression ratio. Are there any specifics as to how these settings correlate with volume?

Thank you for your time,
Zach
  • 0
    TI__Guru**** 189401 points

    Hi, Zach,

    Sorry that we missed your post!

    I took the liberty to split it off the old thread ().

    The section of the data sheet titled, "AUTOMATIC GAIN CONTROL" starting on page 13 has an excellent overview of the operation of this IC.

    The following section, titled, "TPA2028D1 AGC AND START-UP OPERATION" starting on page 21 has an excellent step-by-step tutorial on the programming of the device.

    If you are still having issues after reviewing this, please post the I2C data you are writing to the device, and we will see if we see any obvious issues.

    -d2

  • 0
    TI__Guru 57800 points

    Hi Zack,

    Welcome to E2E, thanks for your interest in our products!,

    We will take a look to this issue and get back to you as soon as possible.

    Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Don Dapkus
    Prodigy 50 points
    Hi Don,

    Thanks for getting back to me. I reviewed the AGC operation on page 13 as well as the startup procedures on page 21. I believe I am following all instructions in those sections correctly. Following startup, I read the values of all the registers which I have confirmed match the defaults listed in table 4 on page 24.

    My intent is to test the maximum volume output of our platform. To do this I turn off AGC (set compression ratio to 1:1), Turn up the max gain to 30dB and disable any output limiting. I then set the fixed gain to a variety of settings with the hope that I would hear a variety of volume levels. The output from this activity confirming that my I2C writes are going through is shown below:

    1. set compression ratio 1:1
    ------------------------------
    I2C read, offset: 0x7, data: 0xc2
    I2C write, offset: 0x7, data: 0xc0

    2. set max gain (30)
    ------------------------------
    I2C read, offset: 0x7, data: 0xc0
    I2C write, offset: 0x7, data: 0xc0

    3. disable output limiter
    ------------------------------
    I2C read, offset: 0x7, data: 0xc0
    I2C write, offset: 0x7, data: 0xc0
    I2C read, offset: 0x6, data: 0x3a
    I2C write, offset: 0x6, data: 0xba

    4. set fixed gain (6)
    ------------------------------
    I2C read, offset: 0x5, data: 0xa
    I2C write, offset: 0x5, data: 0x6

    5. set fixed gain (10)
    ------------------------------
    I2C read, offset: 0x5, data: 0x6
    I2C write, offset: 0x5, data: 0xa

    6. set fixed gain (16)
    ------------------------------
    I2C read, offset: 0x5, data: 0xa
    I2C write, offset: 0x5, data: 0x10

    7. set fixed gain (26)
    ------------------------------
    I2C read, offset: 0x5, data: 0x10
    I2C write, offset: 0x5, data: 0x1a

    8. set fixed gain (30)
    ------------------------------
    I2C read, offset: 0x5, data: 0x1a
    I2C write, offset: 0x5, data: 0x1e

    Note: offset refers to which register is being written/read.

    On each step of changes to the fixed gain, I test the audio by playing a simple sine wave tone. I do not hear any differences in audio loudness (volume). If my intent is to test the audio loudness (volume), am I doing this correctly? Any input would be much appreciated.

    Thank you for your help,
    Zach
  • 0 in reply to Zach Vargas
    TI__Guru 57800 points

    Hi Zach,

    I made some tests with the EVM. The maximum gain you can get can be configured as your register settings. By setting AGC compression to 1:1 and disable the output limiter, you can be able to change the gain of the amplifier in register 0x05. 

    I followed this small sequence and then changed the values of 0x05 to confirm the volume change.

    Reg. 0x07  Data 0xCO 

    Reg. 0x06  Data 0xBA

    Reg. 0x05  Data 0x1E 

    If the Compression is disabled, fixed gain is adjustable only from 0dB to 30dB. 

    Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 50 points
    Diego,

    Thanks for the reply. Looks like I am setting the registers correctly. I have ordered the evaluation module and hope that this will help me out as well. I will keep you posted at to my progress.

    best,
    Zach
  • 0 in reply to Zach Vargas
    Prodigy 50 points

    Hi Diego,

    I reviewed the evaluation board this morning and I have a few questions regarding the results of initial testing. My procedure was the same as on my platform: Set the compression ratio to turn of AGC, turn off output limiting and then adjust fixed gain. See the screen shot below for the settings.

    I noticed that when I set the fixed gain to max (30dB), over the course of several seconds, the volume increases. It appears that the volume slowly increases up to the value of fixed gain as I repeatedly play a sample sound. Could you explain why this change is occurring? I was under the impression that by disabling the AGC, the amp volume could be directly set by fixed gain. To what can I attribute this change in volume?

    Thank you for your help,

    Zach

  • 0 in reply to Zach Vargas
    Prodigy 210 points

    "I noticed that when I set the fixed gain to max (30dB), over the course of several seconds, the volume increases. It appears that the volume slowly increases up to the value of fixed gain as I repeatedly play a sample sound. Could you explain why this change is occurring? I was under the impression that by disabling the AGC, the amp volume could be directly set by fixed gain. To what can I attribute this change in volume?"

    Have you solved this problem ?