DRV8302: DRV8302 application, Final stage fails frequently.

Thilo Binder

Part Number: DRV8302

Hello there,

My almost finished design still makes some problems. It drives a 2000W BLDC Motor in a scooter. I peak = 50A goes down within 10 seconds to 35A continuous current. Voltage 48V, block commutation. The final stage mosfets Q9+Q12 frequently fail. Not in full load operation but during starting up the motor when the PWM and current (soft start) is not very high. I tried 3 different hand made PCBs, and always Q9 and Q12 get shorted completely, R70 also fails.The DRV8302 still works after replacing the Mosfets. I think this could be no accident. The only difference is,

that this part of the final stage is without a shunt resistor. Pin 39 of DRV8302 is directly connected to ground next to the IC. I refered to the famous VESC project, where the pin 39 is connected in the same way. Could that be a problem? Do you have any suggestions?

Regards

Thilo

over 3 years ago

0 Cole Macias over 3 years ago

TI__Mastermind 18900 points

Hello Thilo,

Yes, SLx needs to routed to the source of the FET that the gate is controlling. Essentially, the GLx and SLx can be treated as a puesdo-differential pair where SLx's job is to specifically sense the voltage at the source of the FET. If it is sensing ground near the device, it will never sense the voltage spike that appear directly at the source of the FET and protect against it. This means, the VDS monitors are useless, and the Smart Gate drive architecture doesn't know when it can switch correctly (because the VGS monitors will be incorrect).

This explains why the damage occurs on the specific phase every single time. Please change the design and see if the issue goes away.

Best,

-Cole