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DRV8412: Short Circuit CUrrent Limit

Michael Balourdas
Expert 5455 points
Part Number: DRV8412

Hello,

In the datasheet it says "In CBC current limiting mode, the detector outputs are monitored by two protection systems. The first protection system controls the power stage in order to prevent the output current from further increasing, that is, it performs a CBC current-limiting function rather than prematurely shutting down the device. This feature could effectively limit the inrush current during motor start-up or transient without damaging the device. During short to power and short to ground conditions, the current limit circuitry might not be able to control the current to a proper level, a second protection system triggers a latching shutdown, resulting in the related half bridge being set in the highimpedance (Hi-Z) state."

Is there a defined current threshold where this short condition kicks in and shutdown occurs?

Thanks,

Michael

  • 0
    TI__Guru 55605 points

    Michael,

    In latched mode, there is one comparator that trips within 250ns upon exceeding the limit. This is called LEVEL1 and set via the external OC_ADJ resistor.

    In CBC mode, there are two sets of comparators. The first set (LEVEL1) responds in 400-450ns once the threshold is reached and brings the current down by disabling outputs...this is the same level as latched mode, but the timer is increased to allow the current to be brought down through duty cycle limiting.  If there is a hard short on the output, aLEVEL2 comparator will trip and latch a fault within 250ns....it is quicker than LEVEL1 to protect the device from a hard short.  LEVEL2 is approximately 6A greater than the LEVEL1 threshold set via the OC_ADJ resistor.

    With a hard short, the current will shoot up much higher and much faster with a direct short and this trips a LEVEL2 fault and results in a latched /FAULT even if the device is in a CBC current limiting mode.

    Regards,

    Ryan