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TPA3255: Switching Frequency vs. Input Signal Content

Evan Cornell
Expert 1410 points
Part Number: TPA3255

Does setting FREQ_ADJ to AM2 mode (nominal 600kHz switching frequency) allow for higher input signal bandwidth than Nominal 450kHz switching frequency?

Or is the control loop frequency bandwidth fixed?

If so, what is that bandwidth? I see on the front page of the datasheet that up to 100kHz content bandwidth is a feature, but I don't see a specification for that elsewhere. 

I'm wondering if frequencies above 100kHz are reduced by the bandwidth of the control loop, or if that will cause issues with the switching frequencies, and ought to be pre-filtered before sending to TPA3255.

  • 0
    TI__Mastermind 27590 points

    Hi Evan,

    The bandwidth is the fixed no matter what the switching frequency is set to.  

    I am a little confused with what you mean by 100kHz are reduced by the bandwidth of the control loop.  What frequency are you referring to?

    Best regards,

    Robert

  • 0 in reply to Robert Clifton56
    Expert 1410 points
    So I put bandwidth is fixed regardless of switching frequency. Is that bandwidth characterized anywhere in the data sheet?

    What if the input signal has frequency content above the bandwidth frequency, say at 140kHz.. would that impact switching operation at all, or would the control loop basically just ignore/attenuate that input signal content? I’m trying to understand if I may have instability issues with the amplifier if the input signal has content above the bandwidth of the amplifier.
  • 0 in reply to Evan Cornell
    TI__Mastermind 27590 points
    Are you planning on sending a 140kHz signal or are you more concerned with the noise causing instability into the amplifier?

    If it's noise the amplifier wouldn't have instability issues from that.