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TPS562210A: Soft Start time calculation

K. Sasaki14
Guru 10200 points
Part Number: TPS562210A

Soft start time equation is the below in datasheet,

Tss(ms) = (Css * 0.765 * 0.86) / 6u

When Css is 8200pF, I think Tss is 0.000899(ms). Is this correct although this is 899ns?

I think Tss(ms) is mistake, and Tss(s) is correct. Tss becomes 899us if my idea is correct.

But I think soft start time is about 1.5ms on datasheet Fig, 28 and 29. Is the equation of datasheet correct?

Best Regards,
Kohei Sasaki

  • 0
    TI__Expert 5745 points

    When the Css is 8200pF(8.2nF), the Tss=(8.2*0.765 * 0.86) / 6 (ms)=0.899ms. For the Tss, it means the voltage of SS pin reach to the Vfbth=0.765V, so you can see the Tss in the Fig 28&29 is nearly 1ms. It's closed to the 0.899ms, the equation is correct.