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UCC28070: Soft start capacitance

Mason Noh
Expert 2490 points
Part Number: UCC28070

Hi TI,

Application note shows that Css(soft start) needs to be set to at least the same values as the Czv capacitor or larger.

Please let me know the reason. if Css is set smaller than Czv, what can be problems?

  • 0
    TI__Mastermind 34465 points
    Hello Mason,
    The UCC28070 has an adaptive soft start that overrides the internal reference of the EA with a controlled ramp at start up.
    The integrating capacitor on the voltage error amplifier , CZV also acts like a soft start capacitor as it charges up to its steady state value,
    So therefore you need to ensure that CSS is greater than CZV or otherwise your soft start is set by the error amplifier.
    The adaptive soft start function is described in the data sheet.
    Regards
    John