DRV10983-Q1: DRV10983 - Open Loop Error

Hi Sandesh,

Thanks for posting your question in E2E forum. What is the purpose of running the motor in open loop? In open loop the commutation is blindly done without tracking the BEMF zero crossings. Did you try enabling closed loop? Are you able to get the motor to spin in closed loop or do you see any faults getting triggered? If you see faults getting triggered, can you share the fault code along with the motor parameters and device configuration/register settings? 

Regards,

Vishnu

Hey Vishnu.

I am tuning the motor, so initially according to tuning guide, I am running in open loop. The BLDC fan has max speed(Hz) of 50 Hz. I am running motor in quite high open2ClThr speed. I am able to shift to closed loop. But I am unable to find reason of what might be the cause of that current shape in open loop.

This should be the current shape according to tuning guide. 

Sandesh,

Can you check if the oscillating phase current waveform that you shared is during open loop or closed loop? During open loop, we expect to see constant Phase current that is configured in the open loop current register. I think the oscillating phase current is seen in closed loop. Can you configure FG to "Closed loop only" and plot FG along with the phase current ?

Regards,

Vishnu 

Sure. I will share you the waveforms. However, SysOpt9 Register with address 0x2B has a value loaded 0x3D. It means, I am running it in open loop. 

Here's the waveform with SysOpt9 (address = 0x2B) having a value of 0x4D.

Here's the waveform with SysOpt9 (address = 0x2B) having a value of 0x0D.

Channel three is the FG Pin output and channel 2 is the phase U current waveform.

My configured registers are:

MOTOR_PARAM1    0X4B 
MOTOR_PARAM2    0x5D 
MOTOR_PARAM3    0X2A 
SYS_OPT1               0X40 
SYS_OPT2               0XA8 
SYS_OPT3               0XFE 
SYS_OPT4               0X60 
SYS_OPT5               0XE9 
SYS_OPT6               0X0F 
SYS_OPT7               0X69
SYS_OPT8               0X0F 
SYS_OPT9               0X4D 

Hi Sandesh,

Thanks for sharing the plots. Looks like the load on the fan varies a lot and this causes the current to overshoot. What happens when you enable closed loop? Can you program SysOpt9 to 0x4C and share the FG and phase current plot?

Regards,

Vishnu

Here's the waveform after shifting to closed loop. SysOpt9 Register value 0x4C.

Hi Sandesh,

Waveforms look pretty normal to me. You may slightly increase the open loop current as the closed loop current is higher than the open loop current.

Regards,

Vishnu. 

Hey Vishnu!

The next option of OpenLCurrent in DRV10983 is 1.6A, which is high value for my motor.