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TPA3220: Gain Setting

Y.Ottey
Mastermind 6145 points
Part Number: TPA3220

Dear TI team

I would like you to answer the following questions regarding gain settings.
Our customers have asked us about the Gain error in the table below.

1. Our customers have asked us about the Gain error in the table below.
The Gain error was not shown in the data sheet. Is there any reference data?
(I think that the error of R1 and R2 causes the error of Gain, but if the error of R1 and R2 is not taken into consideration, what will happen to the error of Gain?)

2. Could you elaborate on what the Input Signal Level values in the table below represent?
(I checked the data sheet, but the details were not written.)

Best Regards,

Y.Ottey

  • 0
    TI__Mastermind 27590 points

    Hi Y. Ottey,

    While you are correct that we don't mention the expected gain variations, we do mention that this device allows for a 20% tolerance on the input gain resistor values. I'll check back with design.

    Best Regards,

    Robert Clifton

  • 0 in reply to Robert Clifton56
    TI__Mastermind 27590 points

    Hi Y. Ottey,

    I've talked to the design team and they informed me that the variation of the gain between the devices is small (about 0.25dB).

    As for the second question, we included the input signals to help guide customers to better picking a gain value based on what their expected input signal to the device would be. These values are suggestions for what signal you should put in to get the most dynamic range.

    Best Regards,

    Robert Clifton

  • 0 in reply to Robert Clifton56
    Mastermind 6145 points

    Hi Robert

    Thank you for your reply.

    I would like to ask adding questions.

    1.
    "they informed me that the variation of the gain between the devices is small (about 0.25dB)"
    Is it okay to recognize that the 0.25dB gain variation between devices you answered is ± 0.25dB variation from the Gain value listed in the data sheet?
    Also, is it possible to tell me the conditions when the variation of 0.25 dB was measured?
    (When we told our customers the value of the variation between devices, they asked us about the measurement conditions.)

    2. The maximum absolute rating of the input of TPA3220 is specified as -0.3V to 5.5.
    However, the Input Signal level is written as 2VRMS in the red frame part of the table below.


    When this changes to the Peak to Peak value, it is about ± 2.8V (swing width is 5.6V), and we believe that it may exceed the absolute rating of 5.5V.
    Is this okay?
    (If you like, please let me know if there is a common mode voltage rule for input.)

    Regards,

    Y.Ottey

  • 0 in reply to Y.Ottey
    TI__Mastermind 27590 points

    Hi Y.Ottey,

    1. The tolerance I provided came from the designers. I'll check to see if we measure the tolerance but it might require a discussion offline to share the more specific details as this could contain sensitive information.

    2. The DC bias point right at the pins is 2.5V. So with a peak of 2.8V that would make the signal peak at 5.3V and the lowest point at -0.3V. Right at the edge of the datasheet maximum values but not passing them.

    Best Regards,

    Robert Clifton

  • 0 in reply to Robert Clifton56
    Mastermind 6145 points

    Hi Robert, 

    Thank you for your reply.

    If you can measure the gain tolerance, please measure it.
    (Offline communication is also possible.)

    I would like to ask an additional question
    Gain tolerance is determined by R1 and R2 in the figure below. Is it possible to calculate the estimated value of Gain tolerance from the tolerance of R1 and R2?
    (For example, I would like to know how to calculate the gain tolerance when the tolerance of R1 and R2 is 5%.)

    Regards,
    Y.Ottey

  • 0 in reply to Y.Ottey
    TI__Mastermind 19080 points

    Hi Y.Ottey,

    I think the R1 and R2 is used to bias the voltage of GAIN/SLV pins for a level detection. The device will set the gain on the detected level. This mechanism means the gain accuracy is not directly depending on the resistance accuracy of R1/R2. 

    Thanks!
    Regards,
    Sam