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TPA3126D2: TPA3126D2 Radiated Emissions Issue

Michael Harkins
Intellectual 420 points
Part Number: TPA3126D2

I've implemented a stereo 50W amplifier design using the TPA3126D2 amplifier chip.  I'm having an issue passing CISPR25 radiated emissions.  Initially I was operating the chip at 400KHz, but while the fundamental falls in a gap band of CISPR25, the second harmonic exceeds the class 2 limits by about 12dBuV/m.  I switched to the 1.2MHz operation, but now have an issue with the 5 harmonic failing in the 6MHz band.  Here's the schematic of amplifier section:

Any Ideas?  

  • 0
    TI__Mastermind 19030 points

    Hi,

    If you change to 1.2MHz PWM switching frequency, you need adjust the LC filter to 4.7uH+1uF.

    Do you add inductor on PVCC? this is very important for EMI.

    For 400KHz PWM switching frequency, I suggest you add 4.7uH+10F pi filter on PVCC.

    You can also change 10uH+0.68uF filter to 15uH+1uF.

    The schematic looks fine. EMI is mainly related to PCB layout.

    Regards,

    Derek

     

  • 0 in reply to Yanming Gong
    Intellectual 420 points

    Hi Derek,

    Thanks for the reply.  I didn't want to post the artwork files on an open forum, but if you send me your email address I'll send them to you.  Regarding the inductor on PVCC, I don't see any references to use of this inductor in the data sheet or application information.  Is it one inductor feeding all the PVCC pins?

    Thanks,

    Michael

  • 0 in reply to Michael Harkins
    TI__Mastermind 19030 points

    Hi Michael,

    You can send e-mail to me, my e-mail is: derek-gong@ti.com

    I will reply you as soon as possible.

    Regards,

    Derek