Tool/software:
Hi Sir
Could you help us to review our LM74800 schematic? Our design follow your 200-V Unsuppressed Load Dump Protection Application.
We manufacture about 50pcs of units with LM74800 and find three pcs of units have problem with HGATE FET(Q17001). They was damaged and become resister. We didn't do any testing just normally power on/off them. We still don't find the root cause and if you have any idea please tell us.
Our normal operating condition:
Vin = 9~18V
Max current = 3A (Peak current depend on the battery. It may over 30A)
Below pic is the normal power on sequence measurement.
We choose TPH8R80ANH to be the FET Q1. It is because we don't need to pass the ISO 7637-2. It should be strong enough. We still can't duplicate is issue on my table. If you have any suggestion please tell us.
PS: We already find there is a problem of OVP design. OV pin should connect to Vin not Vout. Our unit will keep turning on and off when Vin is over 30V. We will fix it in next version design.
Thanks
