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Original question:

LM5160-Q1: change the Ron resistance while the LM5160-Q1 is powered on.

LM5160-Q1: Will Vss for soft-start always be 2V?

Hung Ching Hsu
Expert 3086 points
Part Number: LM5160-Q1

Hi Team

I would like to know the range of Tstart when Vout=17V and Css=0.1uF. 

From p.19 of datasheet, I got the formula Css=Iss*Tstartup/Vss to calculate Tstartup.

And also in p.12 of the datasheet says, "soft-start interval ends when the SS capacitor is charged to the 2-V reference level".

Does it mean that Vss will always be 2V  ?

And for Iss, am I correct to use 7.63uA for min. value and 12.5uA for max. value to calculate the range of Tstartup?

If it's correct, the range of Tstartup will be from 16ms (0.1u*2/12.5) to 26.2ms(0.1u*2/7.63u).

All the concern is that, will Vss always be 2V or not.

Is there any error for Vss such as min. value or max value that I should take into account?

Thank you 

Jo

  • 0
    TI__Mastermind 27470 points

    Hi Jo

    you can use 7.63uA for min and 12.5uA as max, but the min and max is not unit distribtution in mass product, it is more like normal distrubtion, so you have very small chance to meet min and max value. 

    the Vss always 2V , min , max value you can use Vref range

    thanks