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TPS7A11: Current limiting functionality

Joselito Go
Expert 3420 points
Part Number: TPS7A11

Hi Experts,

Good day.

Does the current limit circuit here provides overcurrent protection also or just short-circuit protection?

I believed that the current limits circuit is protecting against overcurrent faults too other than the short circuit faults. But in some cases, for example, TPS7A1112PDRVR, the max load current is 500mA but it is providing an output current limit min from 700mA(min for DRV package). So, I didn't get, how it is acting as over-current protection because it should have min 500mA output current limit then. Please insight me more about how here the current limit is protecting against overcurrent faults.


Thanks.
Regards,

Josel

  • 0
    TI__Expert 6570 points

    Hi Josel,

    TPS7A11 has foldback overcurrent protection, which behaves like figure 6.12 in the datasheet:

    Foldback overcurrent protection limits power dissipation instead of output current. You will see the input voltage decrease when the output current is so large that it exceeds maximum power dissipation.  

    I hope this is helpful,

    Erin

  • 0 in reply to Erin Thibeault
    TI__Expert 3420 points

    Hi Erin,

    The graph shows the output voltage vs. output current. Where are the input voltage and input current we are talking about?
    And would you please explain to me furthermore about the current protection this device has.

    Regards,

    Josel

  • 0 in reply to Joselito Go
    TI__Expert 6570 points

    Hi Josel,

    My apologies, I meant the output voltage will decrease if the output current is so high that the device exceeds maximum power dissipation. 

    This device does not abruptly stop the current when current limit is exceeded. There is no overcurrent protection. The current limit on this device is greater than 500mA because foldback overcurrent protection limits power dissipation. When Vout is 90% of its nominal value, in your case ~1V, the output current limit will be 900mA:

    I hope this is helpful,

    Erin

  • 0 in reply to Erin Thibeault
    TI__Expert 3420 points

    Hi Erin,

    What do you mean by there is no overcurrent protection? 
    Is the "foldback overcurrent protection limits power dissipation" not acting like an overcurrent protection? I don't get it.
    By the name itself, it is an overcurrent protection. Would you please clarify?

    Regards,

    Josel

  • 0 in reply to Joselito Go
    TI__Expert 6570 points

    Hi Josel, 

    I mean that foldback overcurrent protection does not behave the same way as brick wall current limit. In brick wall current limit, current abruptly turns off in an over current situation. 

    You are correct, foldback overcurrent protection is overcurrent protection. I meant that current will not abruptly shut off at 500mA, but current and output voltage will decrease linearly so that the device does not exceed maximum power dissipation. 

    BR,

    Erin