5-DRV8825 Questions

For my application I need to drive a stepper motor at 60RPM with 2.5Nm of torque. I have chosen a stepper motor with a maximum allowable torque of 3Nm and a current rating of 0.6A per phase. The stepper motor is aNEMA 16 stepper motor with a 14:1 planetary gearbox so the step angle is 0.131 degrees.

My question is how do I calculate at what RPM the 5-DRV8825 stepper motor driver can drive the stepper motor?

I have read the TI datasheet for the 5-DRV8825 and it says the maximum step frequency is 250kHz, which I am assuming is for the highest microstepping resolution of 1/32 and a maximum driver output current of 2.5A.

Is there a reference table or simple formula that I can use to determine the maximum step frequency at lower microstepping resolutions and lower driver output currents?

Is the relationship between microstepping and torque linear? From what I understand, microstepping reduces torque?[/url]

I would not expect the input step frequency of the driver (ie the 250kHz) to depend on the microstep or the output current setting.

Max RPM for given torque and micro stepping will depend on many variables (driver-, motor-, load-characteristics) and generally I would be rather weary of specs I'm given for cheap motors and drivers to begin with.

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I presume you are aware of the rather terrible speed/torque characteristics of a stepper motor. You might want to ask the supplier of your particular motor for a chart. Also max RPM will depend highly on the voltage you run your motors at.

14:1 at 60rpm would require the stepper motor (Nema16??? ) to run at 840rpm, and that is usually to much for a stepper (they can be run even at 3500rpm with good drives and high voltage but the torque will be very low), so even if it does run, it will not have any torque left.
Basically, drive is not the limiting factor for rpm, it is the voltage the drive can handle, in this case 24V.
Try it, see if it works for you, if not, tell us exactly what you need.