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Over current and current limiting on DRV8332/DRV8312

John Wilkes
Expert 1315 points
Other Parts Discussed in Thread: DRV8332

Hello,

A question concerning the two current protection modes on the DRV8332 device: If my understanding of the data sheet is correct, in CBC mode, the device will attempt to limit current and then latch off if it cannot - how does the device determine that it cannot limit the current, in other words, at what point does the 'second protection system', as the data sheet puts it, kick in?

Also, once the latch off has occurred in CBC mode, does the device enter the same state as if it had latched off in OCL mode, i.e. the RESET_x lines have to be pulled low to re-activate the device?

Cheers,

John.

  • 0
    TI__Guru 55605 points

    John,

     

    Excellent questions and the datasheet can certainly be more clear on this.  

    In CBC mode, there are two sets of comparators. The first set (LEVEL1) responds in ~400-450ns once the threshold (set via external OC_ADJ resistor) is reached and brings the current down by disabling the outputs as described in the datasheet diagrams.  

    If there is a hard short on the output, a LEVEL2 comparator will trip and latch a fault within 200-250ns..../FAULT pin = low.  Note that it is quicker than the LEVEL1 protection in order to protect the device from the extreme case of a hard short on the output when the device starts up.  The LEVEL2 comparator threshold is approximately 6A greater than the LEVEL1 threshold which is set via the external "OC_ADJ" resistor. 

    So, the answer is "YES" to your last question.  It enters the same state as OCL mode and the RESET_x lines have to be pulled low to re-activate the device.  

    Regards,

    Ryan

     

     

     

     

  • 0 in reply to Ryan Kehr
    Expert 1315 points

    Ryan,

    Excellent answers! Thank you very much for your help.

    Cheers,

    John.