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Consideration for hard short circuit events in MOSFET controllers

The question is correspond to any type of MOSFET controller with overcurrent protection. In fact, there are delay between overcurrent detection and MOSFET gate discharge. The delay in range of 1us can lead to MOSFET overstress - dependent of short circuit inductance. What about to add air inductor (and freewheeling diode) to device output to make current rising more slow in case of hard short-circuit event? In most cases this inductor may be no more then 10 uH so it shoul be rather small. In case of parallel MOSFET connetion the common inductor can be separated to individual for every MOSFET. The diode can be selected with rather small current rating - it should handle only big peak currents.

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  • Hi Karl_von_Zhopa,

    Our mosfet controllers are designed to handle short circuit events. Can you tell your specs so we can suggest the right controller?

  • I have selected LTC4380 for my design. By the way my question consider not only for controller, but for power transistor. I think that adding an inductor will make current rise more slower and decrease stress of MOSFET in case of short circuit. The consideration of power MOSFET also decrease - there are no need to handle extreme large current spikes. Also it will eliminate false triggering in case of overcurrent event in devices next by controller.

    My project is electronic fusebox. It's consist of primary protection device based of LTC4380 (protection against reverse polarity, overvoltage and overcurrent) and the local protected power switches. All it controls by MCU with separate power supply. Failure in one of power switches can lead to false shootdown of all system, but inductors can prevent it. Also they give a auxilary EMI filter.

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  • I have selected LTC4380 for my design. By the way my question consider not only for controller, but for power transistor. I think that adding an inductor will make current rise more slower and decrease stress of MOSFET in case of short circuit. The consideration of power MOSFET also decrease - there are no need to handle extreme large current spikes. Also it will eliminate false triggering in case of overcurrent event in devices next by controller.

    My project is electronic fusebox. It's consist of primary protection device based of LTC4380 (protection against reverse polarity, overvoltage and overcurrent) and the local protected power switches. All it controls by MCU with separate power supply. Failure in one of power switches can lead to false shootdown of all system, but inductors can prevent it. Also they give a auxilary EMI filter.

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  • In page 12 of datasheet, it implies product should be able to handle severe short at the output. Please verify this in LTspice and in tests.  The MOSFET should be chosen properly. I don't think the inductor you're suggesting is necessary. You will have the burden of getting right inductor to avoid saturation. With high current and not right rating, the inductor can fail.