Would you please help me understand the part MPQ5069, regarding to its absolute maximum rating on the OUT pin. The data sheet says 30V max while the input is rated at 36V. To my understanding, under normal operation, the part would pass the voltage through. Then the question is, how is the input can be 36V but OUT is only 30V. Can I use this part in a 32V application as a current limiter? 32V>30V really concerns me. I hope you can help me understand more details around this parameter. Thank you!
This can happen through the miracle of inductance. The wiring to the input has some inductance and if current is flowing to the load has some stored energy in that inductance. Now the 5069 decides it has a fault condition and begins to turn off. The voltage developed across that charged up input inductance is V = -Ldi/dt . The result of this is the input to the chip rises in an attempt to force current to flow.
I will restate your response with my understanding to see if I understood you correctly. The moment a fault occurs, IC will cut the connection causing the inductance from the input side to spike up the voltage momentarily. Therefore, the part is really meant to be used under 30V at all times. While 36V rating on the input side is to account for any voltage spike that would occur as mentioned above. The conclusion is really the part should NOT be used in any nominal 30+V application. Please confirm my understanding. Thank you!
Yes, the datasheet states automotive ( 12-14V typically) as the target application. Automotive stuff has this weird "double battery " 24V requirement due to tow truck jump starting voltage, which is what gets it to 30V.