LM25011 behavior at Vout short

Please give some details of your load. What are you powering that causes a short circuit? How long does the short circuit last? Is the short circuit a fault condition or is it a normal load condition?

If it is a fault condition that you need to design for you can add a "hiccup mode" circuit. I can give you details of this circuit if you need one.

The main issue will be the length of time the short circuit lasts and the thermal transient of the MOSFET. You may also need to analyze your output capacitors and make sure they do not overheat during the short circuit.

My application is to test a crowbar circuit during production testing. I need to give 24VDC supply to the DUT (bypassing the input protection fuse), and than apply known voltages at specified points in the circuit to see if the crowbar circuit is working. At certain voltage levels, the crowbar circuit should short the supply. I would measure the current output from the LM25011 to see the operation of the crowbar and at certain point, I need to measure the 500mA to be sure the crowbar fired completely so I can't use a hiccup mode circuit. (Note that the concept was given to me ready and I can't really make any changes, unless they are deemed to be better).

The short circuit would last for max. 2 sec, two times during the test with around 1sec between the two. I can increase the time between the two shorts circuits if this is needed for reliable operation of the LM25011. Also, I can oversize the reverse recovery diode due to its prolonged conduction time.

WHat I'm affraid of is if the LM25011 can handle a sudden hard short circuit. Also, will the current at its output overshoot before reaching back to its set current limit? (this is the primary reason I did not implement analogue current limit).

Thanks

The 500mA is set as a limit to not exceed the SCR specs used in the crowbar while testing. It doesn't need to be strictly this value. I actually first opted for the solution you gave me, but wanted to use something more "neat" (something readily made and tested to work properly).

The only issue I have with the pass transistor option is the current overshoot I may have through the SCR. I did an analogue current limiting circuit but its not fast enough and a surge current of around 7A/50us is seen before the circuit limits to 500mA. I didn't want to go into a complex feedback, compensation circuit (PD or PID) to remove this spike. That's the main reason I opted for this IC cause I had in mind that it had a smooth current regulation without any spikes. At the end, the SCR should be able to handle this spike but I just wanted to go safer in order to be sure that I wont damage the SCR during testing (the DUT is a SIL approved product).

I think I may go with the pass transistor and maybe a series resistor to limit the spike current.

Good to know. Thank you for your help. :)