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TPA2000D1 Output Filter

takishin
Expert 2360 points
Other Parts Discussed in Thread: TPA2000D1

Our customer has questions about TPA2000D1.
I'm posting the questions for a customer:

++++++++++++++++++++++++++++++++++++++++++++++

We are evaluating a TPA2000D1 with a ferrite filter for a speaker output.
The filter is adopted because there was noise by the previous model.

To have the noise radiated from the speaker wire, we're in trouble.

The ground line of the filter capacitor receives a noise.
A frequency of the noise is 480MHz that relates to CPU/SDRAM clock
frequency:120MHz.
The noise is radiated from the speaker wire.
(The length of the wire is 5 inches.)

Questions;

(1)
We're considering to eliminate the filter capacitors only and to leave the
beads.
Are there any problems?

(2)
How much is the maximum current value which flows to beads?
(When choosing beads, we refer to the value.)

++++++++++++++++++++++++++++++++++++++++++++++

Thanks in advance.

Takishin

  • 0
    TI__Guru 57800 points

    Hello Takishin,

    If removing the capacitor solves the problem, perhaps the issue is related to a possible ferrite beard saturation. I would suggest you to take a look to this post. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 2360 points
    Hi Diego,

    Many thanks for your advice.
    That's useful information for me.

    Another question；

    >(2)
    >How much is the maximum current value which flows to beads?
    >(When choosing beads, we refer to the value.)

    When power supply voltage is 5V, how much is the maximum current of Speaker(2W,4ohm)?

    When choosing beads, we refer to the value of Rated Current of beads.

    If you know it, could you let me know?

    Best regards,
    Takishin
  • 0 in reply to takishin
    TI__Guru 57800 points

    Hi Takishin, 

    In the datasheet of TPA2000D1 (page 11), there is a ferrite bead suggestion to use in the output filter. This component has a current rating specification of 2A, so I would suggest to follow this recommendation and use a similar bead. 

    Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 2360 points
    Hi Diego,

    Many many thanks for your answer.

    >Questions;
    >(1)
    I think they should eliminate the beads, because TPA2000D1 is a filter-less audio amplifier.
    Is this right?


    Best regards,
    Takishin
  • 0 in reply to takishin
    TI__Guru 57800 points

    Hi Takishin, 

    Effectively, TPA2000D1 can be implemented without filters due to the device's modulation scheme. However, the filter usage depends of the application and design of the system.

    From Datasheet:

    "Design the TPA2000D1 without the filter if the traces from amplifier to speaker are short. The TPA2000D1 passed FCC and CE radiated emissions with no shielding with speaker wires eight inches long or less."

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 2360 points
    Hi Diego,

    Many thanks for your advice.

    Best Regards,
    Takishin