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ADP1614; Largest SS capacitor allowed?

What is the largest capacitor that can be used on the Soft Start pin of the ADP1614? It contains an internal low-side switch to reset the capacitor in response to certain events (such as thermal shutdown) which implies that there is an upper board on the size of the soft-start capacitor, but the datasheet is silent. I'm looking to use a very long soft start time (~250ms), which, in turn, requires a 1uF cap or so.

  • Hi Jonathan,

    The soft start capacitor Css can not be used for programming the startup time accurately for the ADP1614. The main function of Css of the ADP1614 is to prevent the input inrush current during startup.  Tss = Css*1.23V/5uA is the time that takes the voltage across Css ramping up from 0  to 1.23V. As you seen from Figure 21 in the datasheet, the startup time is about 6mS, not the time calculated by 0.068nF*1.23V/5uA, which is about 16.7mS.

    Best regards,

    Hong

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