Datasheet

TMC2130 DATASHEET (Rev. 1.09 / 2017-MAY-15) 74
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dcStep requires only a few settings. It feeds back motor motion to the external ramp generator, so
that it becomes seamlessly integrated into the motion ramp, even if the motor becomes overloaded
with respect to the target velocity. dcStep operates the motor in fullstep mode at the target velocity
or at reduced velocity if the motor becomes overloaded. It requires enforcing a minimum operation
velocity either by the ramp generator or by VDCMIN. It shall be set to the lowest operating velocity
where dcStep gives a reliable detection of motor operation. The motor never stalls unless it becomes
braked to a velocity below VDCMIN. In case the velocity should fall below this value, the motor
would restart once its load is released, unless the stall detection is used to stop the motor in this
case. Stall detection is covered by stallGuard2.
v
t
dcStep active
VDCMIN
0
V1
VMAX
AMAX
DMAX
D
1
A
1
Nominal ramp profile Ramp profile with torque overload and same target position
overload
Figure 18.2 Velocity profile with impact by overload situation (example)
Attention
dcStep requires that the phase polarity of the sine wave is positive within the MSCNT range 768 to
255 and negative within 256 to 767. The cosine polarity must be positive from 0 to 511 and negative
from 512 to 1023. A phase shift by 1 would disturb dcStep operation. Therefore it is advised to work
with the default wave. Please refer chapter 19.2 for an initialization with the default table.
18.3 dcStep with STEP/DIR Interface
The TMC2130 provides two ways to use dcStep when interfaced to an external motion controller. The
first way gives direct control of the dcStep step execution to the external motion controller, which
must react to motor overload and is allowed to override a blocked motor situation. The second way
assumes that the external motion controller cannot directly react to dcStep signals. The TMC2130
automatically reduces the motor velocity or stops the motor upon overload. In order to allow the
motion controller to react to the reduced real motor velocity in this mode, the counter LOST_STEPS
gives the number of steps which have been commanded, but not taken by the motor controller. The
motion controller can later on read out LOST_STEPS and drive any missing number of steps. In case of
a blocked motor it tries moving it with the minimum velocity as programmed by VDCMIN.
Enabling dcStep automatically sets the chopper to constant TOFF mode with slow decay only. This
way, no re-configuration is required when switching from microstepping mode to dcStep and back.
dcStep operation in STEP/DIR mode is controlled by three pins:
- DCEN – Forces the driver to dcStep operation if high. A velocity based activation of dcStep is
controlled by TPWMTHRS when using stealthChop operation for low velocity settings.
In this case, dcStep is disabled while in stealthChop mode, i.e. at velocities below the
stealthChop switching velocity.