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TPS61087: soft start issue

Part Number: TPS61087

Good morning,

I'm using the TPS61087 boost converter to generate 13.7V starting from 5V input.

As a load I have a big capacitor, 1000uF electrolytic, in parallel to 2x22uF ceramic capacitor.

In order to slow down the initial charging phase, I'm using a 2.2uF Css capacitor.

Unfortunately it seems the soft start feature doesn't work. In attachement the oscilloscope screenshot:

orange - enable signal

yellow - output voltage

blue - input current

The initial current peak does not respect the soft start limitation. It is not always repeatable.

Thank yuo very much for any suggestion or explanation

Best regards


  • Hi Matteo,

    I think the soft start operation works because you can find the output voltage ramps up approximately linearly. The first large inrush current spike is caused by Vout should be charged from 0 to near Vin and the second large current is caused by chip switching. If large output capacitor cannot be changed, could you try increase input capacitor value or add one resistor between input and output for pre-bias?

    Best Regards,

    Eric Yue