LTC4350 with short protection

Hi Yuan.L,

It could be that your Q11 is not appropriate for your design. You could start by reviewing the Q11 parameters or safe operating region.

I check datasheet of Q11. the voltage margin is enough.

Q11 is a 40V 1mΩ MOSFET.

The output of my converter is 12V. Current is 12.5A.

I used the chip and MOSFET with 5V/60A converter succeed. So it's not the current problem. 

Is it about the chip is not appropriate for high output voltage as 12V?

when short protection caused from load  and the converter is good, Converter shut down. then chip shut down. then Q11 shut down. converter get back with no short, because the Mosfet cut the line between the load(short point) and converter. converter start to work. But the load is still being shorted. converter start again and again. then the MOSFET get hot. the MOSFET broke.

Hi Yuan.L,

Its the MOSFET that gets broken and not IC, am I correct? If yes, then there is probably electrical transient that killed MOSFET during the Dc-Dc retries. Please troubleshoot using oscilloscope. LTC4350 can survive up to 17V so it may be safe if there is no transient higher than that. Please double-check your design using LTspice.

Also, this part is not recommended for new design. You may have supply problems if you plan to use it long term. Please consider alternative part LTC4370.

yes, you are right. DC-DC converter have a ability witch is short protection. this protection when short is shut down the converter(output is 0V) and when short disappear the converter is starting again(output is 12V). I think is the open and close some times kill the MOSFET. When LT4350 control the MOSFET opening, the MOSFET is hot. some open and close, MOSFET is hot broken. Because 12V hot swap need much energy than 5V and 3.3V. so I think the LT4350 series not fit the converter(which has short protecion self recovery)