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TPA2005D1: Input resistor(RI) value

Takumi Suzuki1
Mastermind 8430 points
Part Number: TPA2005D1

Hi,

I would like to ask you a question about input resistor value (RI) of TPA2005 as below.

Q)  The specification of "Recommend input resistor value" is 15Kohm(min). (datasheet page4, 7.3 section)

       In case of using lower value, for example 1Kohm, what will happen?

       As 15Kohm is "recommended" value not "absolute", this (Gain>20) will not give any damage to TPA2005, I think.

       Would you tell me the reason why the meaning of min value 15Kohm (Gain <= 20)?

       Are you worried about the audio performance (ex. THD..)?

Thank you for your support.

Best Regards,

     

      

 

  • 0
    Mastermind 8430 points
    Hi,
    Let me ask you one more question, please.
    This issue is from my customer and I got additional information form the customer.
    According to the customer, there seems not to be difference(feeling of sound volume and quality) of output sounds between 15Kohm and 1Kohm.
    They are considering why the output sounds are not degradated in case of 1Kohm.
    Because in case of 1Kohm, the gain is 300 and the signal will be satulated internal the device...

    I would like to get your idea about this phenomenon.
    Thanks for your support.
    Best Regards,
  • 0 in reply to Takumi Suzuki1
    Guru 36490 points

    Hi Suzuki-san,

    I believe that there are two concerns if increasing the gain.
    One is the output offset voltage which may cause the pop noise issue when de-asserting /SHUTDOWN pin to high since it is proportional to the gain.
    The other is the frequency response.
    TPA2005D1 maybe cannot maintain a flat characteristic of the frequency response for the audio bandwidth.
    So, I recommend to measure them.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    Guru 36490 points

    Hi Suzuki-san,

    In addition, please measure the output voltage noise causing the hiss noise.

    Best regards,
    Kato

  • 0 in reply to Takumi Suzuki1
    TI__Mastermind 20085 points
    Hi Suzuki-san,

    Sorry for the delay. That is odd, as you mentioned a high gain would cause a bad audio performance or would saturate the device's output.
    In fact, the gain should be set to 2V/V or lower for optimal performance, if you need a higher input signal you could use a pre-amplifier to get a higher signal.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to Sadanori Kato
    Mastermind 8430 points

    Hello Kato-san,

    Thank you very much for your kind advice!

    I will discuss with my customer.

    Best Regards,

  • 0 in reply to José Luis
    Mastermind 8430 points
    Hi Jose-san,

    Thank you very much for your reply!
    I understood.

    Best Regards,