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TPA3144D2: Radiated Emission of TPA3144D2

yoshiki hasebe
Mastermind 6385 points
Part Number: TPA3144D2
Other Parts Discussed in Thread: TPA3136D2, TPA3140D2

Dear Sirs,

My customer asked us about Radiated Emission of TPA3144D2.

I would like to compare the data of Radiated Emission at FFM and SSM.
Do you have Radiated Emission data on FFM?

Also, do you think that the data of the data sheet is reference data and what I think is right?
I think that it is quite close to the spec line in Horizontal Mode in the data sheet data.
Is there actually a margin?
Therefore, if you have FFM data and SSM data, I think that you can see the improvement effect at SSM.

Best Regards,

Y.Hasebe

  • 0
    TI__Mastermind 24835 points

    Hi Hasebe-san,

    EMI test is a very sensitive measurement. Any change in the test environment or board or configuration could change the test result. e.g. GNDing, speaker wires length, the output filter... The Figure for RE_horizontal in the TPA3144D2 datasheet is based on ferrite bead + 1nF capacitor for the output filter. If you use 2nF capacitors instead of 1nF, the result could be improved. Please find the RE result in TPA3136D2 datasheet, which is based on 2nF capacitors.

    Basically SSM is used for the empression of CE interference, so the result should be similar for SSM enabled or not. Please find some info in this app note

    Best regards,

    Shawn Zheng  

  • 0 in reply to Shawn Zheng
    Mastermind 6385 points

    Hello Shawn-san,

    Thank you for your kindly reply.

    I knew that EMI Test is very sensitive measurement.

    So, I recognize the Test result of datasheet as reference data.
    Is this correct?
    Also, since only data of SSM -> Enable is described in the data sheet, I think that it can compare if SSM⇒Disable (FFM Mode) data exists.
    Do you have measurement data with this FFM Mode?

    This device series is only TPA3140D2EVM.
    TPA3140D2 is also considered the same thing.
    Do you have EMI data with the original circuit constant of TPA3140D2?

    Best Regards,

    Y.Hasebe

  • 0 in reply to yoshiki hasebe
    TI__Mastermind 24835 points

    Hi Hasebe-san,

    Thanks for your explanation. I tried to find the original EMI RE report with SSM disabled on TPA3144D2 or TPA3140D2, but failed. As I mentioned previously, the SSM feature is mainly used to improve EMI CE performance, the RE performance should be almost the same between SSM enabled and disabled. RE performance depends on the edge rate and the overshoot on the PWM output. Because RE test covers higher frequency band and the CE test covers lower band. PWM edge includes lots of high frequency components, and it contributes a lot to the RE result. So it actually makes no sense to compare the RE data between SSM enabled and disabled, becasuse SSM actually doesn't improve RE performance much. 

    Best regards,

    Shawn Zheng   

  • 0 in reply to Shawn Zheng
    Mastermind 6385 points

    Hello Shawn-san,

    Thank you for your quick reply.

    I understand your comments.

    Also I had tried to check interference from TPA3140D2EVM.

    (Because there is no EMI test environment, I placed the search coil on the IC of the EVM and confirmed with the Spectrum Analyzer under the same conditions.)

    As the results, as you said, I was able to confirm the difference in the CE band, but there was almost no difference in the RE band.

    However, since the customer uses the output at a value close to the maximum, I think that the difference of the output filter also affects when compared with the original data.
    (Although it passes naturally in the usual LCFilter, it can be said that it passes even with Ferrite Beads + Capacitor)

    Best Regards,

    Y.Hasebe

  • 0 in reply to yoshiki hasebe
    TI__Mastermind 24835 points
    Hi Hasebe-san,
    Thanks for your update and I'm really impressed by your experimental ability.
    Your understanding is correct, the output filter also affects the EMI measurement result. There shouldn't be any problem in EMI test for inductor + capacitor filter. For ferrite bead + capacitor filter, the higher impedence of the ferrite bead could help improve the EMI performance. And capacitor aslo affects the EMI, e.g. 2.2nF capacitor can impress the EMI better than 1nF.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Mastermind 6385 points
    Hello Shawn-san,

    Thank you for your reply.
    I understand this.
    I will explain it my customer.

    Best Regards,
    Y.Hasebe