• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 81 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

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.

TPS2543: How does current limiting work?

Jacob Wyrick
Expert 6205 points
Part Number: TPS2543

Hi team,

For the TPS2543, how does the current limiting work?

I understand there are two resistors for setting the current limit. One for high threshold, and one for low threshold. The datasheet has a curve and equation for programming these.

What I’m not sure about is how it actually works because UFP determines the current draw. Does the TPS2543 droop the line as the UFP approaches the current limit, or is there some sort of negotiation that I’m not seeing in the BC 1.2 standard?

Thanks,

Jacob

  • 0
    TI__Mastermind 24916 points

    Hi Jacob, 

    You can refer to table 3 on page 28 for more information on which current limit mode is used based on the current mode TPS2543 is in:

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    TI__Expert 6205 points

    Hi Raymond,

    Perhaps I'm missing a finer detail within the table, but the question was less regarding which current limit mode we'll be operating in rather what happens to the current/voltage output as we approach the current limit?

    For example, if we're delivering 5V at 0.8A, but the load current is approaching the 0.9A limit, will we see any change in the output voltage? 

    Or, if we reach the 0.9A limit and the load is demanding more current than our limit will allow, does our voltage then start drooping to 4.9V, 4.8V, or lower?

    Thanks,

    Jacob

  • +1 in reply to Jacob Wyrick
    TI__Mastermind 24916 points

    Hi Jacob, 

    Assuming the connected sink device follows and meets BC1.2 specification, the sink device should not draw more current than the charging scheme negotiated based on the resistor divider across D+/D-. See table below for the max current allow based on port type:

    In a case where the sink device tries to draw more current than allow (over current condition), the device will clamp and maintain a constant current as reduce the output voltage accordingly:

    Thanks and Regards,

    Raymond Lin