Tool/software:
Hi Team
Can you help to review the following schematic? the real PN is LM5050-2.
Customer finds there is a 0.3% probability that Mos Q12/Q13 is damaged when carrying out hot plug in/out in parallel running. lm5050-2 has a probability to damaged as well, the phenomenon is Pin6 performs low resistance, and R48& R49 was burned open-circuit.
Can you give your insight if it is related to SOA of Mos? what's next step recommendation to debug.
Hi Shiven
1. The reason why they add these three components is to suppress oscillation of Vout.
When they carry out hot plug in test, PSU 1 is power on and provide 56V bus, then plugging in another PSU 2. customer found there was a spike on Vout which is over 100V, and will cause LM5050-2 damaged, so they add this RC filter to suppress this spike.
2. They also add C27, R71,R72 for same reason to filter oscillation.
3. I shoot the waveform as following, Channel 1 is 56V bus(Drain), Channle 2 is Vgs, Channel3 is source to GND, Channel 4 is output current. these is a oscillation on Vgs.
Customer found if they change a new mos with higher Vgs threshold mos, the damage issue will disappear(2.8V), the previous oring mos threshold is 1.2V.
I suspect the reason why oring mos or LM5050-2 damage is this oscillated Vgs is higher than threshold voltage of oring Mos to cause Oring mos turn-on.
Do you ever saw this kind of issue? and how to deal with this oscillation?
