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TPS2041B Current Limiter Circuitry

Adam Rosenbeck
Prodigy 40 points
Other Parts Discussed in Thread: TPS2041B, TPS2061C, TPS2068C

Hello all,

This is my first post to the forums so don't beat me up too bad. :)  I was wondering what the scope plot of a 2041B "should" look like.  We currently are hitting our circuit with approx a 2A load for 3ms and we are seeing an overshoot of approx 2A in the current before the 2041b eventually pulls it down to 1A.  How quickly should the part react to a current surge?  Ideally we would like a nice flat current peak at 1A for the duration of our 3ms, 2A pulse.

I hope this makes some sense to someone, I'm pretty new at this :)

Thanks

Adam

  • 0
    TI__Genius 13700 points

    Hello Adam,

    If you could post a scope shot of the current wave form you are seeing that you help immensely.

    Looking through the TPS2041B datasheet the over current threshold is potentially as high as 1.9A which would introduce some initial delay for the active current clamping. This means that there will always be a slight pulse in the output current before the over current even knows it should trigger.

    Since the datasheet does not give the explicit time the device takes to engage the current limiting on the output the best indicator is the OC pin. Looking at Pg. 4 of the datasheet the assertion time of the OC pin is a minimum of 4ms.

    What sort of times are you seeing in your testing?

  • 0 in reply to Ryan May
    Prodigy 40 points

    Ryan,

    First off thanks for helping.  Below is a capture of the current pulse (green trace).  As you can see it takes the entire 3ms pulse we are hitting it with before the limiter gets the current down to around 1.0A.  We were hoping this would happen quicker.

  • 0 in reply to Ryan May
    Prodigy 40 points

    Sorry, it seems it didn't post my screen capture...I'll attach it here.

  • 0 in reply to Adam Rosenbeck
    TI__Genius 13700 points

    Hello Adam,

    Sorry for the delay. The scope trace you have shown makes sense based on the slow over current response of the TPS2041B coupled with its high over current threshold.

    Looking through TI's other offerings I would recommend switching to one fo the parts in the TPS2060x family such as the TPS2061C or TPS2068C. These devices have current limits that are closer to you desired 1A limit which means the over current limit will start to engage sooner and also they have the fasted listed over current response I had seen amongst the USB current limit load switches at 2us which will which is orders of magnitude better than the TPS2041B.

    Let me know if you have any questions.

  • 0 in reply to Ryan May
    Prodigy 40 points

    Thanks for your help Ryan, I might try giving another one of those parts a try and see what happens.

    Thanks for your help!