Hello,
we have made a custom design with the DRV8350S device. We are supplying the DRV in dual supply mode with an external SEPIC converter. So Vm is 12V and Vdrain ist 10 to 15V. The driver is running fine we can do some test eg. But sometimes the DRV get broke. We have found that it alwas happens wehn switching the power supply on or off.
The failured DRV reports then an Vds overcurrent at a Low-Side switch. So i made some measurements with motor windings disconnected. When the device is enabled and all phases of the Motor are switched to ground the phase at the failured low side driver is not switched to ground. GLx is 0.0V and GHx of this phase is 10V but it isnt driven from the INHx pin. INLx is driven high.
The other phases work fine.
I then measured via diode test the gate pins. The GLx pin of the failured phase is shorted to SLx (GND) so i think the GLx low side output MOSFET must be failed. When i think about that, then only a negative voltage could be damage the FETs Diode.
Do you know how we can protect the device against that failure?
Maybe you have another idea why the driver fails?
Thank you very much,
Florian
