Hello,
We are designing a stepper motor driver using the controller DRV8711. The circuit is very similar to the evaluation board DRV8711EVM. Today, we discovered that the connected motor stalls at a rather low rotational speed (~10Hz) when we set the bit RDIR in the CTRL register to 1, i.e. reverse the direction. With the default configuration (RDIR=0), the motor runs well up to ~65Hz. Apparently, it does not matter, whether the configuration reads RDIR=1 and DIR=L or RDIR=0 and DIR=H, the DRV8711 simply does not like the reverse direction. The mechanical behavior of the motor (any asymmetry in the coils, in the stator or in the rotor) does not play any substantial role. If we reverse the polarity of one of the motor coils, the motor spins in the opposite direction, but the abovementioned issue remains, i.e. if the DRV8711 reverses the direction, the motor stalls. Even if we replace the motor by another one or use the evaluation board DRV8711EVM, the observed issue remains the same - the driver DRV8711 does not work well with the reverse direction.
We operate the motor typically with 1/2 to 1/16 microsteps. With full steps, there seems to be no difference in either direction.
Our observations indicate that the asymmetry issue is caused by the motor controller DRV8711 and not by any asymmetry in the remaining hardware. Is there any known asymmetry in the internal design of the DRV8711 that could explain this behavior?
Thanks!