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TAS5766MRMTEVM: TAS5766MRMTEVM

Rick Kukulies
Prodigy 100 points
Part Number: TAS5766MRMTEVM
Other Parts Discussed in Thread: TAS5766M

This question concerns audio performance and EMI. On the TAS5766MRMTEVM there is an section using conventional LC demod filter and another using ferrite beads. How do the two compare in audio performance (do the ferrite contribute to audio distortion?) and EMI performance.

  • 0
    TI__Mastermind 24835 points
    Hi Rick,
    We are looking into this and will get back to you later.
  • 0
    TI__Guru 52115 points
    Rick,

    We usually recommend LC filters in TAS5766M designs since it would be much easier to pass EMI tests if a LC filter is used.

    You can find the following recommendations about when to use ferrite bead output filter on Page 48 of TAS5766M datasheet.

    The TAS576xM can be used with a small, inexpensive ferrite bead output filter when speakers are placed with
    short internal wires and supply voltages are 12 V or lower, for systems with longer wires or higher than 12V
    supply voltage LC filtering is recommended.

    Regarding the audio performance difference, I will check whether we have some exiting data.

    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 100 points

    Andy;

    My application is for !@V and short, twisted speaker wires (6 inches). So this should be a candidate for ferrite beads. Has TI done EMI tests on the TAS5766MRMTEVM?

    Rick

  • 0 in reply to Rick Kukulies
    Prodigy 100 points
    Andy;

    My application is for 12V and short, twisted speaker wires (6 inches). So this should be a candidate for ferrite beads. Has TI done EMI tests on the TAS5766MRMTEVM? Sorry for the correction!
  • 0 in reply to Rick Kukulies
    TI__Expert 6720 points
    Rick,

    As you know, EMI performance is highly related to system board design. Normally TI has expecial EMI testing board to verify the device EMI capbility, not directlly use EVM board (which is used for general audio performance checking).

    Generally speaking, we do not recommend ferrite beads solution if EMI performance is critical requirement. For example, CE and RE performance with LC filter will provide ~15dB better margin than ferrite bead one.

    Thanks,
    Matthew
  • 0
    Guru 140200 points
    Hi Rick,

    the ferrtite bead is only able to filter out the highest harmonics of switching, because the low frequency inductance is very small. L5=CIS21P300 of EVM has a low frequency inductance of only 0.16µH. The inductance of L1, on the other hand, is 4.7µH and gives a 30 times better filtering compared to L5.

    Ferrite beads cannot handle very well high currents. They go into saturation very quickly. And ferrite beads which can handle high currents, do not have high inductances.

    Kai