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What does this infomation mean?

shizunori
Prodigy 250 points
Other Parts Discussed in Thread: TPS54331

SwitcherPro displayed the following information when I have simulated a schematic with TPS54331. What does this information mean?? Can I use this result with no trouble?

Total Derated Capacitor value 20uF is small enough that the dominant pole frequency 5.7Khz is within 2 decades of 1/2 the switching Frequency. This can be avoided by raising the total capacitor value to 81uF.

  • 0
    TI__Intellectual 2710 points

    There is a pole at the dominant frequency and a double pole at ½ the switching frequency.  These residues cause phase loss extending one decade either side of these frequencies.  Ideally the closed loop crossover needs to occur where the phase is maximized.  That will be in between 1 decade above the dominant pole and 1 decade below ½ the switching frequency (where the phase is not diminished by either residue).  If the dominant pole and ½ the switching frequency are less than 2 decades apart, the crossover will be at a frequency where the phase is reduced.  This may not be a problem depending on the phase boost required and the ESR zero frequency, but as the dominant pole moves higher relative to ½ the switching frequency, phase eventually decreases so much that there is not enough phase boost available in the compensation network to provide adequate phase margin.

    Hope this helps.

    Thanks,

    Hetal.

  • 0 in reply to Hetal
    Prodigy 100 points

    which capacitors make up the total capacitance?  thanks