I'm using the DRV8825 in a product design, but am having some trouble with it. I'm using a 3.9V 600mA NEMA8 stepper motor. I want to drive the system off of 12V because it's available and convent. However the DRV8825 will only function when I use 9V or less on the motor voltage input. Above 9V input the fault pin immediately trips.
I know that stepper motors can preform better with higher input voltages so that they can change their currents faster. The DRV8825 is rated for 45V motor input. I'm not sure why the internal overcurrent protection is limiting my motor input voltage. The datasheet says that it's internal OCP is separate from the external motor current limiting setup.
Why is the OCP tripping and is there anything I can do to use a higher input voltage? Does it have anything to do with the decay mode?
Thanks
My setup is as follows:
- Step and Dir are driven by 3.3V signals
- Enabled is controlled, 3.3V or Gnd, Gnd when running
- Sleep is controlled, 3.3V or Gnd, 3.3V when running
- Decay pin is floating
- Mode pins are floating (but I've tried using the to try different stepping modes)
- Reset is tied to the 8825's 3.3V output
- ISense A and B each have a 0.2 ohm resistor
- A and BVref are set through a 10k and 2.21K resistor from the 8825's 3.3V otuput for a voltage of 0.6V (for 600mA)
- 10nF cap between CP1 and CP2
- 0.1uF cap between VCP and VmotorA and B
- 0.47uF cap between 8825 3.3V out and gnd