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SwitcherPro TPS54226 Softstart Calculation is incorrect

Ryan Henderson
Intellectual 980 points
Other Parts Discussed in Thread: TPS54226

It appears that the SwitcherPro model for the TPS54226 is incorrect when it comes to calculating the soft-start capacitor value.  Seems to be 10x too high when compared to a manual calculation in the datasheet.

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    TI__Expert 3875 points

    Hi Ryan,

    Thanks for identifying this issue. By default, SwitcherPro uses a 3.3nF capacitor on the SS pin for the TPS54226. This is the same value as used in the datasheet example and EVM. However, SwitcherPro does calculate an incorrect slow start duration. It should be 1.26ms for a 3.3nF cap. Instead, SwitcherPro shows 12.38ms. So, the calculation is ballpark off by an order of magnitude.

    I will ask the developers to look at the code that calculates the cap value from the advanced inputs form and the code that computes the slow start duration after part selection.

    Thanks,
    Michael

    -- 
    Michael Krasnicki
    Analog eLab
    Texas Instruments