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TPA3111D1-Q1: EMI/EMC issue with CE and Radiated

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Replies: 8

Views: 166

Part Number: TPA3111D1-Q1

Hi team,

I have used Audio amplifier having part number TPA3111D1 and i am facing issue in compliance related to Conducted emission and Radiated emission.

1) In Conducted Emission, When Speaker started to work then i can easily see noise level is going high and it is passing just on marginal level but i am sure if speaker will work for long time then it will cross the limit.

2) In Radiated also, when speaker started to work then at 37.772MHz & 68.862MHz frequency it is crossing the limit and noise level is going up to 55.89dBuV/m & 48.74dBuV/m respectively.

I have used ferrite bead and Capacitor combination at the output of amplifier. What is the meaning of filter less audio amplifier?

Best Regards

Sumit Ranjan

  • hello Ranjan,

      for TPA3111-Q1, it is proposed to use LC filter instead of ferrite bead to pass EMC.

    regards

    Linda

  • In reply to Xiaolin Qin:

    Hi Linda

    What is the purpose of giving an example of ferrite bead in datasheet and also what is the exact meaning of filter less class D Amplifier?

    What is the recommended value for LC combination?

    Best Regards

    Sumit Ranjan

  • In reply to SUMIT RANJAN:

    Hi Ranjan,

    From the CE result, it can pass CE test. We suggest to add one filter on PVCC power supply to suppress the noise. 

    What's output power?

    Do you add snubber on output?

    And can you send the bead spec to us?

    If possible, please also send the schematic and PCB layout to us for review.

    Thanks!

    Regards,

    Derek

  • In reply to Yanming Gong:

    hello, Ranjan,

        do you have further upper Derek asked info to share to us? We want to further look at your setup details.

    Regards

    Linda

  • In reply to Xiaolin Qin:

    Hi Derek & Linda,

    I was  traveling so it delayed. Here is the required data.

    1) I have used ferrite bead having part number "PZ1608U330-3R0".

    2) We are using 10W speaker but since my input voltage is 9V so i believe it will be less than 10W and near by 7W.

    3) I have kept snubber circuit after ferrite bead and Cap combination but that is no mount. 10E and 470pf is ok to use? It will be helpful?

    4) I have attached Schematic of Auio amplifier section. On layout side, PDF of each layer will work for you of each layer or Gerber (with marked area)?

    ----- > I am still looking for the meaning of filter less audio amplifier?

    Audio Amplifier Ciruit.pdfPZ1608U330-3R0F.pdfPZ1608U330-3R0*F" from SUNLORD MFG.

    Best Regards

    Sumit Ranjan

  • In reply to SUMIT RANJAN:

    Hi Ranjan,

    I saw the impedance of the bead is 33ohm@100MHz, it is a little low for EMI.

    I suggest to use 300ohm or 600ohm@100MHz. High impedance bead is better for EMI.

    Regards,

    Derek

  • In reply to Yanming Gong:

    Hi Derek,

    This ferrite change is sufficient for conducted and radiated or we need to add something more on speaker amplifier side?

    Best Regards

    Sumit Ranjan

  • In reply to SUMIT RANJAN:

    Hi Ranjan,

    From the RE test report, the spur is around 30MHz. I am afraid that is the harmonic of LC resonant frequency.

    You can try using high impedance bead, and you can also add 33nF capacitors on output, close to audio output connector.

    Regards,

    Derek