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TPA3112D1: Relationship between the PLIMIT voltage and output voltage amplitude(Vp-p) on table 2

Shota Mago
Expert 7000 points
Part Number: TPA3112D1

Hi team,

My customer will use TPA3112D1 and provided some questions regarding PMIM as follows

  1. In section 7.3.3 PLIM, datasheet states that "The PLIMIT circuits sets a limit on the output peak-to-peak voltage. ~ This virtual rail is 4 times the voltage at the PLIMIT pin." However, Output Voltage Amplitude (Vp-p) doesn't match 4*PLIMIT Voltage on Table 2.
    How Output Voltage Amplitude(Vp-p) was calculated on Table.2?
  2. Also, how Ouptut Power(W) was calculated on Table.2?
    Is it possible to derive based on equation (1)?

Best regards,

Shota Mago

  • 0
    TI__Mastermind 19330 points

    Hi Shota,

    The calculation is for unclipped application. Table 3 data has some clipped output power.

    Regards,

    Derek

  • 0 in reply to Yanming Gong
    Prodigy 40 points

    Hi Derek

    I am a customer of Shota Mago.

    Table3 shows the contents of DC Detect for input.
    Table2 shows the contents of the function to limit the output power.
    Are Table 3 and Table 2 related?

    I want to know is how to limit the output power to 1.5W.
    Please tell me how to find the PLIMIT Voltage to limit to 1.5W and how to find the resistor connected to PLIMIT.

  • 0 in reply to user6251258
    TI__Mastermind 19330 points

    Hi,

    I am sorry, I checked error datasheet. 

    The correct is Table 2 which data has some clipped output power.

    DC fault has no relation to PLIMIT feature.

    Regards,

    Derek

  • 0 in reply to Yanming Gong
    Prodigy 40 points

    I will ask you again.

    The items in Table 3 are listed as AV (dB) and Vin (mV, differential). Contents is about Vin.
    I think it has nothing to do with the output power from the content of the item.
    Or is the content of the item wrong?

    I want to know is how to limit the output power to 1.5W.
    Please tell me how to find the PLIMIT Voltage to limit to 1.5W and how to find the resistor connected to PLIMIT.

  • 0 in reply to user6251258
    TI__Mastermind 19330 points

    Hi,

    Yes, Table 3 only describe DC detect fault. Table 2 is the example data, but it includes clipped data.

    For your application, Pout=1.5W, if the load impedance is 4ohm, impedance of trace and inductor is 0.1ohm, we can calculate Vp according to below calculation, which shows on page 13 in datasheet:

    1.5W=(((4/(4+2*(0.24+0.1))*Vp)^2)/2*4

    0.24ohm is Rds impedance; The calculation power 1.5W is for unclipped power.

    Then Vp is 4.06V. VP = 4 × PLIMIT voltage, so PLIMIT voltage should be 1.02V;

    That is calculated data.

    Regards,

    Derek 

  • 0 in reply to Yanming Gong
    Prodigy 40 points

    Hi Derek,

    Thank you.

    Regards,