DRV10974: The DRV10974 stops after starting for a few seconds

Hi Cherry,

Vishnu will get back to you on Monday!

Thanks,

Matt

Hi Cherry,

Let us look at each resistors.

CS resistor:

What is the maximum motor current rating? Refer to the below table and choose a resistor that is close to the maximum rated current of the motor.

RMP resistor:

7.32 kΩ sets very low acceleration, higher startup time and think this should be okay for now.

ADV resistor:

Since the inductance of the motor is too low, can you ask customer to try lower lead times (between 50 µs and 250 µs) as shown below? 

Also, can you request customer to share the phase current plot? I would like to check what fault is getting triggered.

Regards,

Vishnu

Hi Vishnu,

Thanks for your reply!

Vishnu Balaraj said:

CS resistor:

What is the maximum motor current rating?

The current rating of the motor is unknown. Phase DC resistance: 5.2 ohms between U/V.

Vishnu Balaraj said:

ADV resistor:

Since the inductance of the motor is too low, can you ask customer to try lower lead times (between 50 µs and 250 µs) as shown below? 

The customer tries to lower the lead times to 20k, but the problem still exists.

:

Vishnu Balaraj said:

Also, can you request customer to share the phase current plot? I

NOTE: Since the customer has no current probe, the phase current is indirectly measured by measuring the voltage across the resistor in 1-phase series with a 1-ohm resistor as follows:

Phase current 1 (when the motor starts to run):

Phase current 2 (when the motor starts to stall):

Phase current 3 (when the motor starts to stall):

Thanks and expecting the updates!

Best Regards,

Cherry

From the phase current plot, it looks like the device triggers "Abnormal BEMF" fault. Can you set the current limit to 200 mA and try lead time from 50 us to 250 us?

Regards,

Vishnu 

Hi Vishnu,

Thanks for your reply!

The latest updates are as follows:

The customer found the original drive module of the motor and tested to assume that the motor is rated for 10 to 20 mA. But the DRV10974 minimum current can only be set to 200 mA, can this chip be used to drive this motor? Or are there other models recommended?

And I have updated your suggestion to the customer, if there is anything new I will forward to you asap.

Thanks again!

Best Regards,

Cherry

Hi Cherry,

Vishnu will respond soon.

Thanks,

Matt

Hi Cherry,

I would recommend trying out all the lead times as suggested in the previous post. Also, please refer to this tuning guide for detailed procedure on tuning all three resistors. 

Regards,

Vishnu

Hi Vishnu,

Thanks for your reply. The latest updates as follows:

R-RMP = 7.5K, R-CS = 7.5K (~200mA), R-ADV set 18k, 22k, 30k, 33k respectively.

But the phenomenon is still the same as before, and the phase current waveform is the same as before, and stops after running for a while.

Thanks and expecting your update!

Best Regards,

Cherry

Cherry,

Please note that all the resistors have a tolerance of ±1% only. Make sure you pick resistors that are within this accuracy. Can you connect a 200 kΩ potentiometer on ADV pin and set the pot to all the resistor values listed in below table and check the performance at each value? 

Regards,

Vishnu

Hi Vishnu,

Thanks for your reply!

The customer would like to confirm if the ADV resistance value be exactly the same as the resistance value in the table you provided.

If there is a deviation, should the result fall between two gears?

The customer has followed your suggestion make the following changes:

Keep R-RMP=7.5K, R-CS=7.5K(~200mA)

R-ADV is set to 10k, 15K, 18K, 22K, 30K, 33K, 39K, 51K, 62K, 68K, 75K, 91K, 110K, 130K, 150K, 180K.

The motor could run for seconds under all the R-ADV resistors, and then stall. Occasionally the motor jitter after several stops, but does not turn (and not every stall at the same resistance), when the phase current frequency is high (T=520us).

Could you please help check this?

Thanks a lot!

Best Regards,

Cherry 

Hi Cherry,

Yes, the resistor values should be same as mentioned in the datasheet with  ±1% tolerance. Can you recommend customer to try DRV10983? This device provides more options to configure and tune.

Regards,

Vishnu 

Hi Vishnu,

Thanks for your reply!

The latest updates as follows:

1. The customer has checked internal block diagram of DRV10974, and found that RMP ADV CS input is 3 ADCs, with different resistors, and the chip's internal should be a different digital code, so even if use a resistor with a bias, they will fall into one of the two adjacent bits. And when the customer changes the CS and RMP resistors, also finds the change in motor current and acceleration.

2. Follow your recommendation, the customer still would like to figure out the root cause of the issue.

3. And there is also a problem that DRV10983 is out of stock and is hard to get. So the customer wonder if it's okay to use DRV10975.

Thanks!

Best Regards,

Cherry