DRV11873: Lock Detection functionality

Na Na,

Yes, false lock detection can occur at all multiples of FG frequency near 101.6Hz.

This is possible for all DRV11873 devices.

Thanks,

Brian

Hi Brian

Thank you for reply.

I captured some wave forms with EVM which is default settings.

Would you answer the following questions?

1. 

The following image shows FG signal while motor spinning.

A frequency of FG is approximately 119Hz and it would match to internal sampling clock frequency with 101.6Hz + 30%.

Why does the motor spin without lock detection even though the frequency of FG within a range of 101.6Hz + 30% of internal sampling clock?

2.

When a FG signal reaches up to 980Hz, motor lock is detected and same operation is repeated like following.

Should we regard this behavior is caused of DRV11873 errata described in SLVA778?  Or any other reason?

Could you tell us your view?  We want to achieve 1KHz of FG. (It means RPM = (1KHz * 60) / 6 = 10000rpm)

BestRegards

Na Na,

Sorry for the delay. Message got lost in holiday activities.

1. For the false lock to occur the FG frequency must be close to the internal clock frequency. It's the internal clock frequency that can vary by +/-30%. So it is possible that the motor will function without false detect inside the +/-30% range of the clock frequency just poses a risk that you might see false lock detect.

2. Yes, any multiple of the clock frequency can cause the false lock detect. Since 1kHz is near the center of the clock frequency it is quite likely that you are hitting the false lock detection described in SLVA778.

Thanks,

Brian