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Original question:

TPS1200-Q1: TPS12000-Q1 RISCP Calculation Formula Discrepancy (Datasheet vs. TI Excel Sheet)

TPS1200-Q1: Tolerances on ISCP quantities of TPS12xx and TPS48xx?

Dan Quixoté
Prodigy 70 points
Part Number: TPS1200-Q1


Tool/software:

Due diligence for ourselves and automotive customers requires worst-case analysis. To that end, what are the tolerances of the 2uA and 19mV quantities in the Riscp formula below? 

  • 0
    TI__Genius 11260 points

    Hi Dan, 

    2uA is an internally derived reference current, and 19mV is the comparator offset. 

    The inaccuracies associated with these value are incorporated in the SCP threshold from the EC table. 

    Where V_SCP = ISC x RSNS

    You can use the RISCP values in the datasheet to determine the %error and add that to the VSCP value calculated based on above equation. 

    Thanks, 

    Sarah

  • 0 in reply to Sarah Raines
    Prodigy 70 points

    >> "2uA is an internally derived reference current, and 19mV is the comparator offset."

    Yes - just looking for explicit tolerances on those two quantities.

    >> "The inaccuracies associated with these value are incorporated in the SCP threshold from the EC table."

    I s'pose so. Given the min/typ/max's on the 3-ish operating points, I guess I can do matrix log math to tease out the individual tolerances [It'll collapse to simple ANOVA] - so I can figure out the worst-case tolerancing of the operating points were looking at for two products using this IC. It's just more work than I'd prefer.

  • 0 in reply to Dan Quixoté
    TI__Genius 11260 points

    Hi Dan , 

    I see. The values above is what we can provide. The method outlined is how we suggest customers determine worse case accuracy for their system. 

    Thanks, 

    Sarah

  • 0 in reply to Sarah Raines
    Prodigy 70 points

    Math results for the world on this, using the table data (9 eqns / 9 unknowns) -

    In the first row where Riscp=28k, Isrc = 1.6 / 2.0 / 2.4 uA min/typ/max, and Voffset = 0.0152 / 0.019 / 0.0228 V min/typ/max

    In the 2nd row where Riscp=10.5k, Isrc = 1.65 / 2.0 / 2.35 uA min/typ/max, and Voffset = 0.014675 / 0.019 / 0.023325 V min/typ/max

    In the 3rd row where Riscp=500, Isrc = 1.7 / 2.0 / 2.3 uA min/typ/max, and Voffset = 0.01415 / 0.019 / 0.02385 V min/typ/max