LT8648S , paralleling , SS pins

the data sheet for the LT8648S , shows that two can be paralleled , to give higher current.

The SS pins on other LT DCDC parts that can be paralleled, 

    normally have their SS/Track pins connected together,

Can i double check please what to do with the two SS pins on the pared parts ?

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  • 0
    •  Analog Employees 
    on Dec 28, 2020 7:07 AM 1 month ago

    Hi,

    On the data sheet of LT8648S, it is stated that the SS/Track pins may be left floating if the soft-start feature is not being used, that's why the SS pins are just tied together and not connected to any soft-start capacitor. A capacitor on the SS/Track pin will program the ramp rate of the output voltage. Typical applications of parallel operations on LT DCDC parts often tie the SS/Track pins with a capacitor connected to ground in order to ensure that the soft-start output of the two regulators are the same with the other.

    Regards,

    Siglo

  • Thank You

    so to be clear

       For the parallel option, the SS pins of the two LT8648S need to be tied together, and one capacitor to ground to implement the soft start function,

    With two LT8648S SS pins joined, how does that affect the value of the SS capacitor to select ?

          do we have an equation or table as to the value of Capacitor and the soft start time please when  two LT8648S are paralleled like this ?

  • 0
    •  Analog Employees 
    on Jan 4, 2021 2:52 AM 1 month ago in reply to andm

    Hi,

    Yes but if you don't need to use the soft-start option, you can just tie them together as recommended in the data sheet. Usually, when operating in parallel, you will tie the SS/Track pins and tie it with a capacitor connected to ground to control the soft-start time with the value of the capacitor. Apparently, we don't have an equation for the value of the capacitor available in the data sheet for two LT8648S. 

    Regards,

    Siglo

  • Thank you 

        Yes need to have some control over the start up, 

              Pity no data in the data sheet on this .

    Please close 

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