Use the SS input to limit input current

I want to use the LT3958 boost converter

24V input and 70V output.

Most important, the input current shall never exceed 1A at 24V, even when this means reducing the voltage at the output.

Can I use the SS (SoftStart) input to do that?

I have used LTSpice and put a voltage divider from INTVcc to GND, center to SS (10K, 1K) and it seems to simulate ok.

Before I make a PCB... does anybody has an idea why this may not work, or even has a better idea.

  • 0
    •  Analog Employees 
    on May 7, 2018 8:57 PM

    When the Vout is lower than the Vin during startup, the current can flow from the input to the output uncontrolled, even if the SS cap is very large, and thus the input current could exceed 1A. If that's unacceptable, you might want to consider an IC that provides input current regulation such as LT8705. Page 40 of the LT8705 datasheet shows an example for input current limit.