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Original question:

UCC28950: how many consecutive cycle by cycle current limit thresholds need to be seen before controller enters shutdown...

UCC28950: SLUSDB2B, Fig. 6-15 (Timing Diagram of Soft Start): What does the 25uA annotation under the Normal Operation line at 4.65V mean

Nitish Agrawal
Expert 1595 points
Part Number: UCC28950

Tool/software:

Hello Mike,

SLUSDB2B, Fig. 6-15 (Timing Diagram of Soft Start):  What does the 25uA annotation under the Normal Operation line at 4.65V mean?

I couldn't respond to your post from earlier today (regarding the number of consecutive cycles in current limit before shutdown), hence I am asking this as a related question.

Sincerely,

Nitish Agrawal

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    TI__Guru* 85926 points

    Hello,

     

    The 25 uA is the pull up current on the soft start capacitor.  When it reaches 4.65V it will not source current any more.  If you are hitting cycle by cycle current limit of 2 V the soft start capacitor will discharge based on figure 16-15.  If you don't trigger over current hiccup mode and you stop hitting cycle by cycle current limit the soft start capacitor will recharge to 4.65 V with the 25 uA shown in the diagram.  There is also 1 k ohm resistor that will help with pulling the soft capacitor as well when the voltage at the SS pin is 3.7 V or greater,

     

    Thank you for interest in Texas Instruments (TI) products.  If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

     

    Regards,