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TPA6304-Q1: EMC issue in 200kHz 20MHz 60MHz 100MHz 200MHz

Joe Ji
Expert 3950 points
Part Number: TPA6304-Q1


Hi team

Customer use TPA6304-Q1 in ford project, but cannot pass the EMC test use the suggest design, here are some questions:

1. What will cause the EMC issue in 20MHz 60MHz 100MHz 200MHz when there is no overshoot and ring in the output stage? How can I solve that?

2. When customer test the EMC in Iveco, after the amp power on they can test a 200kHz radiation, will the amp can generate the 200kHz radiation directly or it may cause by the DCDC power supply?

here is the EMC test waveform:

after add the magnetic beads in the output stage, the EMC problem can be solved, but it can cause over current issue in some time.

when I test the output stage of 6304 the waveform is good without any overshoot and ring.

Thank you  

Best Regards

Joe

JUL 27

  • 0
    TI__Guru 52150 points

    HI Joe

       May I ask that what Standard we used to test the EMC, clearly it's not the same as CISPR25 that most of the customer would use? Could you please give us the serial number of this Standard? So we can doing some research into it.

       For your problem, the frequency from 20MHz to 60MHz, is mostly from switching frequency's high order component. For this area, some method you could consider: 1. Use a better shield inductor, and keep the distance between inductor and your connector as far as possible, and also shield your connector. 2. Keep the LC filter loop as small as possible on your PCB. 3. Keep PVDD decoupling capacitor close to devices PVDD/GND pins.

      For 100MHz, it is likely from the output cable. Do we have the 10nF capacitor placed very close to the connector on the PCB? This would help.

      For 200MHz, in your waveform, it doesn't over the Standard, correct? If customer find any noise, they are only possible from the overshoot and undershoot of switching behavior. Add snubber if you think necessary. 

      To testing the overshoot/undershoot, you need to take care of the method as below document. Also they would only appear when you start output power, you can't find anything in idle state. 

    Voltage Spike Measurement Technique and Specification.pdf 

  • 0 in reply to Shadow He
    TI__Expert 3950 points

    Hi shadow

    I attach the standard in this post, the standard is created by ford.福特EMC标准.pdf

    for 20M 60M and 100M I will check the design with customer.


    Joe Ji said:
    when I test the output stage of 6304 the waveform is good without any overshoot and ring.

    for the two EMC point between 200MHz, one is lower than 200M one is higher than 200M, at first I think it may caused by overshoot and ring, but you can see the test picture, there is almost no overshoot and ring in the output stage, the test is following the document instruction, but anyway the EMI in this range is not very high.

     

    Joe Ji said:
    2. When customer test the EMC in Iveco, after the amp power on they can test a 200kHz radiation, will the amp can generate the 200kHz radiation directly or it may cause by the DCDC power supply?

    will the amp cause 200kHz emc issue? I think it may related to the power supply.

    Thank you

    Best regards 

    Joe

    JUL 28

  • +1 in reply to Joe Ji
    TI__Guru 52150 points

    Hi Joe

      I checked the results at our side, it's better at 200MHz. Below picture test under 4*1W condition, 4ohm load. Since no obvious overshoot been captured, there indeed should be clean at 200Hz. There's some layout may slightly affect this area, like the LC filter loop, and the position of PVDD decoupling cap. We could check if it is possible to optimize.