DRV8452: Questions about the number of revolutions of motor.

Hi Nakai-san,

Thank you for posting in this forum.

Kazuya Nakai59 said:

Q.
DRV8452 datasheet says that the maximum input frequency of the step signal
of DRV8452 is 100kHz.

Currently, when using the DRV8452 at high speeds, it seems like it cannot keep up with high frequencies.
There is no problem at 16000pps. (16000 x 1/32/200 = 2.5rps = 150rpm)
But at 64000pps, the drive current waveform seems strange. (64000 x 1/32/200 = 10rps = 600rpm)
They think it depends on the motor they use. But they want to know what is the cause of the strange occurred at 64kHz
even though DRV8452 says maximum frequency is 100kHz or higher.

Are the causes the motor inductance and back electromotive force of the motor?

Yes this is correct. Motor inductance and BEMF at high speeds would cause severe current distortion and motor stall is VM is not sufficient to overcome these at high speeds. 

This is the general behavior of stepper motors at high step rates when VM supply voltage is not sufficient to overcome the back EMF (BEMF) generated at high step rates and unable to push the target current via the motor windings. This depends on motor specifications R and L and BEMF constant, VM supply voltage, target IFS, step rate, accelerate rate, load inertia and load torque. Can you share these details including the stepper motor datasheet.

A common solution for this behavior will be to increase the VM supply voltage. Assuming the customer was testing with 24 V they can try the same at 48 V. Customer should notice an increase the maximum step rate they can achieve without stalling with higher VM.

Kazuya Nakai59 said:

Is there any countermeasure to increase the step clock frequency?

Increasing VM and/or reducing IFS can improve this situation. In some cases changing the motor to lower inductance coils specification might resolve to some extent. Please refer to these posts one and two. Thank you.

Regards, Murugavel