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TAS5720L: Output filter

Part Number: TAS5720L

Looking at the schematic of the evaluation board they recommend 15uH + 680nF when using the M version, but when the L version is used the L is a ferriet (NFZ2MSM181SN10L) and the C is 330pF. I can't find no explanation about the output filter. 

Off course I can do what is told, but I try to understand why. Why is a ferriet used instead of the 15uH and what is best?

For the NFZ2MSM181SN10L a can't find an graph, but if it is 180 ohm @100MHz, it  seems to me that it doesn't filter a lot on 48kHz.

  • Add: I use a 8 Ohm speaker, with a sort cable (10 cm), max 2W is needed.
  • Add: What modulation is used? In the evaluation board C(BTL) is not populated so I assume it is BD modulation?
    With 15u and 680n, f ~ 50kHz
  • Hi,

    Ferrite beads are mainly used for suppressing EMI and are not able to filter switching ripple as much as an inductor does.

    The use of ferrite beads can be found in lower-cost applications but for higher audio quality, we would suggest using an inductor.

    Thank you!

    Best regards,
    -Roy Hsu
    Texas Instruments
  • Hi Roy,

    Thanks. Just like I thought, but why is the ferriet recommended when the L-version is used? Not a big deal, I already use a 15uH inductor.

    What modulation is used by the TAS5720L? AD or BD? Is seems to be BD if I look at the filter, but it is not in the datasheet.

    Met vriendelijke groet, with best regards, Mit freundlichen Grüßen,

    Rody van der Meel,
    Hardware engineer



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    Van: "Roy Hsu" <bounce-4807416@mail.e2e.ti.com>
    Aan: AudioAmpsForum@mail.e2e.ti.com
    Verzonden: Maandag 10 april 2017 21:12:15
    Onderwerp: Audio Amplifiers Forum: TAS5720L: Output filter

     

    A Message from the TI E2E™ Community
    Texas Instruments

     

    Roy Hsu replied to TAS5720L: Output filter.

    Hi,

    Ferrite beads are mainly used for suppressing EMI and are not able to filter switching ripple as much as an inductor does.

    The use of ferrite beads can be found in lower-cost applications but for higher audio quality, we would suggest using an inductor.

    Thank you!

    Best regards,
    -Roy Hsu
    Texas Instruments

     

     

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  • Your understanding is correct. TAS5720L/M is a BD device.