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TPS54335A: The frequnecy tolerance of TPS54335A

takahiko yokota
Mastermind 7135 points
Part Number: TPS54335A
Other Parts Discussed in Thread: TPS54308

Hi

The frequency tolerance of TPS54335A is guaranteed ±20% over  operating free-air temperature range.
Are there the reference data of the frequency tolerance if the temperature range is 0~80℃?
Best regards,
Yokota
  • 0
    Mastermind 7135 points

    Please let me ask further questions.
    The switching frequency tolerance is about ±20% according to 6.7 Switching Characteristics.
    What is the accuracy of resistance in this characteristics?
    I think the switching frequency tolerance is about ±2.5% in figure 4.
    Is the the switching frequency tolerance ±20% considering the individual difference?
    Best regards,
    Yokota
  • 0
    TI__Expert 4035 points
    Hi Yokota-san,

    Yes, +/-20% tolerance have conditions of Ta=-40C to 105C and Vin=4.5V to 28V. this parameter is test guaranteed in final test. However, the test is configured with test mode test, which means it won’t have switching noise impact.
    So it could be possible to have slightly higher/lower frequency under higher Vin case where switching noise is heavy.

    Could you share with us why you are care some much about the fre variation? What’s the acceptable range?

    BRs,
    Ryan
  • 0 in reply to takahiko yokota
    TI__Expert 4035 points
    Hi Yokota-san,

    When selected a RT resistor, the frequency is setted, and the frequency tolerance is about ±20%. the individual difference of RT have impact to the frequency tolerance. Based on my experience, i think the accuracy of resistance is not very good but could be accepted in normal application.

    BRs,
    Ryan
  • 0 in reply to Ryan Hu (BSR-MV)
    Mastermind 7135 points

    Hi Ryan-san

    Thank you for the answer.
    My customer design the audio application.
    So he worry about the frequency tolerance.
    May I think the accuracy of resistance is about 5%?
    Best regards,
    Yokota
  • 0 in reply to takahiko yokota
    TI__Expert 4035 points

    Yokota-san,

    5% i think is resonable, TPS54335A could adjust the operating frequency, so it should have an enough margin.

     we have another part expecial for audio application, TPS54308, could RTM by 8th June, if you are interested, i could send the draft datasheet to you by mail.

    BRs,

    Ryan

  • 0 in reply to Ryan Hu (BSR-MV)
    Mastermind 7135 points

    Hi Ryan-san

    Thank you for the proposal.
    But my customer use TPS54335A because they have used it.
    They use TPS54335A the following conditions.
    What is the frequency tolerance under these conditions?
    Or are there the calculation or simulation method?
    ・Vin=21V, Vout=3.7V, Iout=1.21A, Fsw=300kHz, Rrt accuracy=1%
    ・Vin=21V, Vout=5V, Iout=0.53A, Fsw=990kHz, Rrt accuracy=1%
    Best regards,
    Yokota
  • 0 in reply to takahiko yokota
    TI__Expert 4035 points
    Hi Yokota-san,

    Sorry, as i known, we have no such a calcualtion tool for the frequency tolerance. there is a calcualtion equation 4 in the datasheet, but the equation is a fitting formula. For worse case, i think seting ±25% frequency tolerance totally is good enough and then keep away from the amplifier working frequency for audio application.

    BRs,
    Ryan