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TPA3110D2 Input Impedance Variation

Sadanori Kato
Guru 36540 points


Hi,

We have a question regarding the input impedance.
Our customers have evaluated the input impedance.
When the GAIN0 and GAIN1 were setting to high(36dB gain setting), the input impedance was 12.8kohm.
We found that the input impedance is 9kohm +/- 20% on page 16 of the data sheet.
The resistance value are different more than 20%.
Is the target specification correct?
Could you please tell us this reason?

Best Regards,
Kato

  • 0
    TI__Guru**** 189401 points

    Hi, Kato-san,

    Can you describe how you measured the input impedance?

    -d2

  • 0 in reply to Don Dapkus
    Guru 36540 points

    Hi Don-san,

    Thank you for your reply.
    We will explain to you the evaluation method regarding the input impedance.
    We have connected the register 30kohm to RINP(pin 12), entered a signal to the terminal of this resistor.
    Our verification circuit diagram is as follows.

    We calculated the internal resistance using the input amplitude and the amplitude on the 12pin.
    Can you understand about evaluation method of the input impedance?

    Best Regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Mastermind 37045 points

    Hi Kato-san,

    I measured the input z and it was measured at 8.4K Ohms. Attached is my measurement setup sketch.

    Input is 1KHz, 1Vrms.

    Precision RC Box was used to obtain 0.5Vrms across the R (~8.4K Ohms).

    Voltage across the R is feed to AUX-25 and AP filter to filter out noise. AP Amplitude reading is 0.5Vrms. 

     

    reg,

    Paul.

     

  • 0 in reply to user5276421
    Guru 36540 points

    Hi Paul-san,

    Thank you for your cooperation.
    We will tell your evaluation result to our customers.
    We believe that the cause is measurement accuracy.
    Thank you for explaining it carefully.

    Best Regards,
    Kato