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TPS3808: one question about the delay time of TPS3808

Oliver Ou
Intellectual 2845 points
Part Number: TPS3808

Hi,

Cusotmer uses TPS3808 and found the delay time with below equation is not well matching the electrical table on datasheet.

for example,  when CT=180nF, the typical delay time should be 1.03nS with equaiton 1, but the typcial dealy time is 1.2nS in 

the table.  Also the typcial delay time is same for CT=180nF and CT=100nF in the table. 

Customer wants to know why? Can you help to check and give some comments?  Thanks.

  • 0
    TI__Genius 9375 points

    Hi Oliver,

    In general, the equations that are made for the datasheet are made from a design perspective and could differ from the actual characterization values that are measured for the electrical characteristics table. This is also why we specify a range (0.7s to 1.7s). There are factors that could vary this value a bit (capacitor tolerance values, board design, temperature) but it should fall between this range. The calculated value (1.029s) thus does fall in this range.

    To your second question, I believe this is a misunderstanding as if you look to the unit column to the right, the RESET delay time for 100 pF is 1.25 milliseconds and for 100 nF this is 1.2 seconds.

    Thanks,

    Abhinav.