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TPA3251: PFFB of TPA3251

aggil liang
Expert 2660 points
Part Number: TPA3251

Hi 

There are some question about PFFB of TPA3251. The input audio signal is single-end, TPA3251 is setted to BTL mode.

When we use the circuit of figure 2, it happen to POP noise when the AMP shutdown or the Pin18 'reset' is pulled down . But the circuit of figure 1 don't happen this.
pls. give some solution to eliminate pop noise when shutdown when use PFFB way.

Another, when using the PFFB, Is capacitance of C311,C312,C313,C314 same , 100P ? Or C311=C314= 300P, C312=C313=100P ?

When we design different Op-Amp gain compensation, how we decide these capacitance ?

  • 0
    TI__Mastermind 20830 points

    Hi Aggil,

    I apologize for the wait.  The popping only happens when you are shutting down/reset the system?  This is the first time I have heard of a popping issue when using PFFB.

    Also in case you haven't seen it, we have a fairly new Post-Filter Feedback AP note that is a very comprehensive guide for PFFB. The AP note also goes into how to find the Op amp capacitor values (C311, C312, C313, and C314) but, you will want to keep all four capacitors the same value.

    Hopefully this help!

    Best Regards,

    Robert

  • 0 in reply to Robert Clifton56
    Expert 2660 points

    Hi Robert

      thanks for your reply. 

     This issue only happen when shutting down or reset pin pull down. 

    Anohter , As the input sigle-end signal change to diff signal using the OPA, the circuit is different with the file you linked, pls. help to check again. 

  • 0 in reply to aggil liang
    TI__Mastermind 20830 points
    Hi Aggil,

    Could you send me an oscilloscope shot of the pop you are seeing?

    For single-ended mode you will want to set U300A and U301B to unity gain (default configuration you had in figure 1), to keep the signal truly balanced. Right now your signal is becoming unbalanced. I don't believe that would be causing the popping issue however.

    Regards,

    Robert