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TPS22990: Calculation method of delay time

Liu Yang
Expert 7475 points
Part Number: TPS22990

Hi Team,

The calculation of Rise Time is shown on page 17 of datasheet.
But there is a slight difference between table1 and my calculation as below:

tR=(0.011 * VIN + 0.002) * CT + 4.7 * VIN + 7.8
In case of VIN=5V, CT=10000pF
My result: tR=601.3us
Table 1: tR=598.5us

The calculation of Power Good is the same:
tPG,ON=(0.013 * VIN + 0.04) * CT + 4.7 * VIN + 129
In case of VIN=5V, CT=10000pF
My result: tPG,ON =1202.5us
Table 2: tPG,ON =1239us

Can you tell me the reason for the difference?

Best Regards,
Tom

  • 0
    TI__Genius 13300 points

    Hello Tom,

    The formula is a linear equation generated to give a general idea of the timing. It will slightly vary from measured values depending on input and load conditions. The values from the table won't exactly line up with the equation values due to the fact that the equation was generated from all Vin and CT data points to allow the user to input their VIN and CT values into the equation.

    Regards,

    Kalin Burnside