I am starting the development of a board using the DRV8818 stepper controller however it keeps shutting down the output drivers. I am not entirely sure why this is happening as I don't believe that any short circuits / over current or over temperature protection is kicking in.
The stepper motors I am using are rated at 0.8A 12V with a measured winding resistance of 16 ohms. I have verified that there are no short circuits between the motor phases (measures resistances between A+/A-/B+/B- while connected to the driver).
When I apply power to the driver (with no pulse inputs) power is applied to the motor for approx 15 seconds then the DRV8818 drivers seem to turn off. When power is applied I can not turn the shaft (as expected).
If I apply a step signal to the driver it seems to disconnect the output drivers immediately (1-2 seconds).
To verify that I am not having any over current issues I have inserted a 10 ohm resistor in series with the 24V power supply I am using. This will limit the maximum current to the DRV8818 to about 2.4A. With this resistor in place I am still having the same issues (its not possible to have an over current lockout in this case, right?). The average voltage across this resistor is 5.3V (530mA).
I can also touch the the DRV8818 chip and it still feels cold so thermal lockout is also not likely.
Do you have any idea what could be causing the output drivers to shut down?
I should also mention that I might have a poor board (grounding) layout as the voltage across my 0.20 ohm sense resistors seems to have about 50mV peak to peak noise present. At the full motor current of 0.8A it should be 160mA, so the only issue I can see this causing is that the noise might be limiting the current to a lower value than the 0.8A I set it to drive.
Edit: I should note that I am sending the control signals to the driver from a micro controller powered from the same 3.3V supply as the driver.
