TMC5161 DATASHEET (Rev. 1.01 / 2018-NOV-20)
95
17 dcStep
dcStep is an automatic commutation mode for the stepper motor. It allows the stepper to run with
its target velocity as commanded by the ramp generator as long as it can cope with the load. In case
the motor becomes overloaded, it slows down to a velocity, where the motor can still drive the load.
This way, the stepper motor never stalls and can drive heavy loads as fast as possible. Its higher
torque available at lower velocity, plus dynamic torque from its flywheel mass allow compensating
for mechanical torque peaks. In case the motor becomes completely blocked, the stall flag becomes
set.
17.1 User Benefits
Motor
–
–
–
–
–
never loses steps
Application
Acceleration
Energy efficiency
Cheaper motor
works as fast as possible
automatically as high as possible
highest at speed limit
does the job!
17.2 Designing-In dcStep
In a classical application, the operation area is limited by the maximum torque required at maximum
application velocity. A safety margin of up to 50% torque is required, in order to compensate for
unforeseen load peaks, torque loss due to resonance and aging of mechanical components. dcStep
allows using up to the full available motor torque. Even higher short time dynamic loads can be
overcome using motor and application flywheel mass without the danger of a motor stall. With
dcStep the nominal application load can be extended to a higher torque only limited by the safety
margin near the holding torque area (which is the highest torque the motor can provide).
Additionally, maximum application velocity can be increased up to the actually reachable motor
velocity.
torque
MMAX
microstep
operation
dcStep operation - no step loss can occur
additional flywheel mass torque reserve
m
a
x
.
m
o
t
o
r
t
s
a
f
o
r
q
e
t
y
m
a
r
g
i
n
u
e
MNOM2
dcStep extended
application area
MNOM1
Classic operation area
with safety margin
0
velocity [RPM]
MNOM: Nominal torque required by application
MMAX: Motor pull-out torque at v=0
Safety margin: Classical application operation area is limited by a certain
percentage of motor pull-out torque
Figure 17.1 dcStep extended application operation area
Quick Start
For a quick start, see the Quick Configuration Guide in chapter 22.
For detail configuration procedure see Application Note AN003 - dcStep
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