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Original question:

TPS3808: True Accuracy of TPS3808

TPS3808: RESET Delay Time Accuracy No Capcitance?

Filipe Rubinstein
Intellectual 931 points
Part Number: TPS3808

Tool/software:

Hi Team, 

I am digging into the RESET delay time accuracy for the TPS3808 when I came across another thread listing the breakdown of how the 40% accuracy variance is calculated. 

E2E - TPS3808: True Accuracy of TPS3808

According to Jesse, the 40% accuracy variance includes an assumption of a 20% tolerance capacitor, yet this 40% accuracy variance remains the same even when removing the capacitor from the equation. Can you provide any guidance as to why this is or how much of an impact does the Ct capacitor truly make on the reset delay time? 

Regards,

Filipe Rubinstein

  • 0
    TI__Mastermind 18970 points

    Hi Filipe,

    The 40% is for the worst case consideration plus guard band. With proper implementation using low leakage, low tolerance capacitor you will not see 40% variance across temperature. But it is recommended to design for 40% as per the datasheet value.

    Jesse   

  • 0 in reply to Jesse Villanueva
    TI__Intellectual 931 points

    Jesse, 

    I wanted to bring this thread back up. 

    Can you provide better clarity on why the RESET delay variance is still 40% even if you do not have a CT capacitor?  Assuming a best case of having proper layout, what would the RESET delay variance be? 

    Regards,

    Filipe Rubinstein

  • 0 in reply to Filipe Rubinstein
    TI__Mastermind 18970 points

    Hi Filipe,

    The major contributors for the variance are component and device tolerance and application ambient temperature. The 40% accounts for corner cases with an additional guard band, this value was derived during device characterization when the device was developed. Unfortunately, we do not have the break down of the characterization data on which factor played into the 40% value. 

    Jesse