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TPA6211A1-Q1 EMS(Electro Magnetic Susceptibility)

Jin Kyung Han
Expert 1520 points
Other Parts Discussed in Thread: TPA6211A1

Hello

I would like to have solutions how to avoide the EMS issue. The TPA6211A1 generate noise by adding radiated RF

signal. I find out the reason of generating noise, it is demodulated through inducing Power Line for TPA6211A1.

The Test RF signal is AM noise modulated by carrier 20Mhz ~ 400MHz and its base signal is 1KHz. I can listen the

1KHZ signal through the Speaker which connected to the TPA6211A1. The length of the power cable for TPA6211 is 2

Meter. My opinion on solution is using Common Mode filter for Power Cable.

Please let me know how to prevent TPA6211A1 as AM demodultor.

 

  • 0
    TI__Expert 5380 points

    We have assigned this post to one of our apps engineers. They will respond to you recently.

  • 0
    TI__Genius 14890 points

    Jin,

     

    Yes, additional filtering on the power input to the device is very important for reducing noise. What capacitance is currently on the power input?

  • 0 in reply to Alexander Scheuermann
    Expert 1520 points

    Alexander

    The target Boadr is TI's EVM BD. I think the induction points in the Device may be input / output / power.

    Do you have any PCB design guide as well as Common mode filter schematic?

    Let me know how to put the common mode filter to the PCB and well immuninty PCB design guide.

    Thanks and Best Regards

  • 0 in reply to Jin Kyung Han
    TI__Genius 14890 points

    Jin,

     

    The first step in TDMA noise troubleshooting is figuring out how the noise is getting into the system. There are three common injection/coupling paths to check regarding TDMA noise:
    Inputs
    The TDMA noise could be coupling into the system along the input traces leading to the amplifier device. To check this, try disconnecting the amplifier's input capacitors from the PCB and AC GND the inputs of thedevice (AC GND the input pins as close to the device as possible). If the TDMA noise goes away, then the noise is likely coupling onto the inputs and transmitting through the amplifier.
    In this case, ensure that the input traces are buried under a GND plane. Also, ensure that the shielding for the audio portion of the product is independent of the antenna and RF portions of the phone (or receiver). Finally, make sure that the input traces are not crossing or overlapping with any other board level traces that could carry the TDMA noise – particularly supply traces or RF traces.
    Headphone only OR class D only
    If the TDMA noise is heard on the HP only or the class D only, it is likely that the inputs to the amplifier are not to blame. In this case the noise could be getting into the system by either directly coupling onto the output traces, or by coupling onto a power supply line that only connects to the HP or class D of the amplifier.
    In this case, ensure that the output traces of the affected output are buried under a GND plane if possible, and that they are not exposed to any RF traces. Also, see if the noise can be improved by increasing the value of decoupling capacitors for the supply lines to the affected output (such as HPVDD, or VBatt – assuming these are supplied via separate references).
    Regarding the decoupling capacitors, please ensure that all decoupling caps are connected to the top GND layer. Sometimes capacitors are grounded to an inner layer using vias. This is not recommended as it can increase the AC impedance between supply and ground, which can make TDMA noise issues worse.
    Headphone AND class D (but not input traces)
    If the TDMA noise is present on both the HP and class D amp, but does not seem to be injected through the input traces, check the supply references that are used by both systems (primarily, check Vbatt. Try improving the decoupling on this line by increasing the value of the decoupling cap, and ensure that it is well grounded in the system). If this third situation is the case, the signal could also be coupling onto both sets of output traces, or onto the inputs after the input capacitors (not likely – but possible). Try shielding these areas from the antenna and see if the noise goes away.
    Lastly, related to all of these points, check how the amplifier's GND balls are connected to the system. The best performance TDMA noise performance is usually achieved by connecting the GND ball(s) to both the inner GND layers and to the top GND layer. This provides the lowest impedance AC path from the supply lines to system GND, and should improve TDMA noise in almost all cases.
     
    You can also take a look at this app note which has some additional information.
  • 0 in reply to Alexander Scheuermann
    Expert 1520 points

    Alexander

    The App note is a very usefule document becuse I clear the issue.

    Thanks

  • 0 in reply to Jin Kyung Han
    TI__Genius 14890 points

    Jin,

     

    Great! Glad it helped