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WEBENCH results do not match with datasheet calculation

lev nemets1
Intellectual 435 points
Other Parts Discussed in Thread: TPS43061

Dear Sir or Madam

We are going to use TPS43061 Controller. We found that some results from WEBENCH design do not match with TPS4306x_BOOST_CALCTOOL_REVB.xls tools (and Datasheet calculation). For example, WEBENCH gives cross-over frequency 15kHz, Phase Margin 50°, Gain Margin 10dB (good margin).

We used component's value from WEBENCH design in TPS4306x_BOOST_CALCTOOL_REVB.xls and got cross-over frequency 8.7kHz, Phase Margin 53° and Gain Margin minus 9dB (excitation). It is not small mismatch, but completely different result.

So, which tools we should trust?

We tried to make a simulation model for this controller, but it datasheet does not have enough information:

1. Parameters of slope compensation signal

2. Parameters of Error Amplifier output: Does it sink current or source current or both and what is the its output current limits.

We would really appreciate your help

 

  • 0
    Prodigy 250 points

    Hi lev nemets1:

    First, I am just a beginner also a passenger in this forum.

    The following is some opinion of mine.

    Loop gain and phase curve (bode plot) is based on the L-C characteristic of the schematic topology and the Vout Vs Vin

    (suppose typically used the numerator as the Vout, denominator as the Vin ) where same as labeled in the application schematic of the TPS43061 datasheet.

    There are so many parameters which could affect the final result .

    Let's say the parameters is all the same as used in both tools.

    The application of TPS43061 is DC to DC converter.

    In actual implementation, I think maybe lower the input voltage ripple would take effect if finally you find the output voltage ripple is too large to be acceptable.

    some opinion for your reference.

    Thank you.Have a good day.

  • 0
    TI__Genius 14455 points
    Hi Lev,
    The datasheet calculation for compensation component selection ignores the effects of slope compensation. You can refer to page 27 of the datasheet. The WEBENCH calculations take the slope compensation into consideration and that is the major reason why this would be different. We are further looking into why the excel tool is different from the WEBENCH calculations. We will let you know once we have an answer on that.

    Regards,
    Gerold