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Noise on TPA3111d1 supply lines

Jens Kuhrt
Prodigy 20 points
Other Parts Discussed in Thread: TPA3111D1, TPA3136D2

We are having noise problems in the supply lines which are causing FCC EMI issues (radiated and conducted).  

Attached waveform shows spikes (measured between PVCC and PGND terminals) that seem to be the cause of the problem.

Also attached is the schematic we are using.

Any ideas/suggestions would be welcome.  We have already spent quite a bit of time on this with not much progress.

Regards,

Jens

  • 0
    Prodigy 20 points

    How important is track symmetry around the OUTP and OUTN lines ?
    Due to layout constraints, we have approx 5mm variation in track lengths between the TPA3111 and the FB5/6 beads.  The beads are approx 10-15mm from the IC and mounted on opposite side of a 6-layer PCB.
    Could this be causing the PSU spikes ?

    The bypass caps on PVCC are all nice and close to the IC.

  • 0 in reply to Jens Kuhrt
    TI__Expert 5000 points

    Hi, Jens

             Do you have any EMI filter on PVCC or your power supply is a AC-DC module which convert 110V AC to PVCC? If you test CE with DC power supply, I would to say it is very hard to pass CE test without any EMI filter on PVCC.

             What is the PVCC value? If the PVCC value is lower than 14.4V, I recommend you use TPA3136D2 instead, this is pin2pin with TPA3111D1. TPA3136D2's CE har more than 15dB improvment compare with TPA3110/11D2.

                For RE test, recommend to use larger impedance ferrite bead ( for example : NFZ2MSM601SN10) and 2.2nF capacitor to test RE again. This will achieve more margin for RE. 

                For CE , maybe one method is adding a EMI filter (LC filter) on the PVCC

  • 0 in reply to Peter Cao
    TI__Expert 5000 points
    What is more, suggest to use speaker to do the test, not just a resistor....