Other Parts Discussed in Thread: DRV832X, DRV8350, DRV8323, DRV8353, DRV8320, MCT8316Z, MCT8315Z
Hi everyone,
We are using DRV8306 to develop a custom motor controller. During no-load spinning of the motor the controller works good, but when we try to increase the mechanical load, the motor shuts off and a fault is latched on the nFault pin. Since the only fault that latches is the Gate drive fault, we assume that this is the issue.
The datasheet states that Gate drive fault can be caused by to slow rise/fall times on the gates of the mosfets. So we measured the gate signals when the fault triggers. Here are captures for each phase separately.
Brown - nFault,
Blue - Phase voltage,
Green - Gate Low (G_L),
Red - Gate High vs. Source High (G_H vs. S_H)
Phase A
Phase B
Phase C
None of the gate signals need more than 4000ns to rise/fall which is the limit for gate drive fault triggering. So why is the gate driver fault reported?
The fault seems to always trigger on at the same time in the swithing period, meaning that there is one particular even which triggers it and is not random.
The Idrive is set to maximum setting so that the rise/fall times are as short as possible.
We have noticed that by lowering the Idrive setting, and consequently slowing the rise/fall times, the Gate Drive Fault is not reported anymore, however this raises our losses to unacceptable levels and we would like to remain on the high Idrive setting.
I would also like to mention that the motor that we are using has hall sensors positioned for CW rotation, meaning that they are not in a neutral position between the phases but are slightly tilted towards one phase.
I have attached our Altium project with the schematics and PCB for your reference.
So in summary - we are experiencing a Gate Drive Fault when loading the motor. By reducing the Idrive setting the fault is not reported anymore. What can be the cause of this and how can we fix it?
Thank you!
Samo
Altium project file:
