drv8308: Motor stops working, Register 2A shows value of 0x4F (OCP, CPOC, OTS, UVLO and RLOCK = 1)

Hi Marco,

It is difficult to determine the reason without examining what occurred prior to the fault. The device reported several faults.

It is recommended to set the scope to capture the phase currents and the VM voltage prior to the fault. This should provide clues to what fault occurred. If you have a temperature probe you can add this to determine if the device is overheating.

Hello Rick,

thanks for your reply.

Unfortunately, I just recognized a bug in the code for evaluation of the register content. I suppose, that the right value that suddently appears is 7F (Mask corrected from 4F -> 7F) -  seems that the drv8308 is not responsive.

I have seen this value (unmasked = 65535), when device isn't powered. In the faulty case, the other driver still have power above minimum threshold (in my project, there are three motors each driven by drv8308, which are all connected to the same voltage source).

I monitor the motor current but not per phase. The summarized current is < 300 mA.

I have logged some information, perhaps it's helpful for you:

motor=1   Speed1=     0   Speed2=   -97      I=   170     pwm=  -51     st=0  pos=27110
motor=1   Speed1=  -200   Speed2=  -148      I=   306     pwm=  -41     st=0  pos=27108
motor=1   Speed1=  -100   Speed2=  -146      I=   168     pwm=  -41     st=0  pos=27107
motor=1   Speed1=  -100   Speed2=  -142      I=   199     pwm=  -42     st=0  pos=27106
motor=1   Speed1=  -100   Speed2=  -139      I=   226     pwm=  -32     st=0  pos=27105
motor=1   Speed1=  -100   Speed2=  -133      I=   141     pwm=  -32     st=0  pos=27104
motor=1   Speed1=     0   Speed2=   -88      I=    94     pwm=  -39     st=0  pos=27104
motor=1   Speed1=  -200   Speed2=  -129      I=    92     pwm=  -30     st=0  pos=27102
motor=1   Speed1=  -100   Speed2=  -127      I=   112     pwm=  -29     st=0  pos=27101
motor=1   Speed1=     0   Speed2=   -68      I=   121     pwm=  -41     st=0  pos=27101
motor=1   Speed1=  -100   Speed2=  -118      I=   209     pwm=  -26     st=0  pos=27100
motor=1   Speed1=  -100   Speed2=  -118      I=    38     pwm=  -24     st=0  pos=27099
motor=1   Speed1=  -100   Speed2=  -108      I=    59     pwm=  -40     st=0  pos=27098
motor=1   Speed1=  -100   Speed2=  -111      I=   165     pwm=  -40     st=0  pos=27097
motor=1   Speed1=  -100   Speed2=  -109      I=   197     pwm=  -55     st=0  pos=27096
################### drv8308-fault: 4f ###################
motor=1   Speed1=     0   Speed2=   -97      I=     0     pwm=  -55     st=79 pos=27096
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27096
motor=1   Speed1=   100   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097
motor=1   Speed1=     0   Speed2=     0      I=     0     pwm=  -55     st=79 pos=27097

Speed1 is calculated from hall-signals

Speed2 is calculated from time between slopes on TACH-signal (FGOUT)

I is the measured current [mA]

st is the value of register 2A masked by the faulty value 4F

Pos is position calculated from hall-signals

Update cycle is 10 ms

The current seems to be Ok.

Do you have any idea ?

Best regards

Marco