TMC389 Datasheet, PDF (33/48 Pages) TRINAMIC Motion Control GmbH & Co. KG. – three phase stepper motor driver

TMC389 DATASHEET (V. 1.15 / 2015-OCT-27)
33
12.4 Limits of stallGuard2™ operation
Please bear in mind, that stallGuard2™ will not operate reliable at extreme motor velocities: Very low
motor velocities (e.g. for many motors less than one round per second) generate a low back EMF in
the motor and make the measurement instable and dependent on environment conditions like
temperature, etc. Inappropriate conditions will also lead to extreme settings of SGT and low response
of the SG result to the motor load. On the other hand, very high motor velocities, where the driver is
not able to drive the full sinusoidal current into the motor coils also will lead to a low response in the
SG result. These velocities are typically characterized by the motor back EMF reaching the driver
supply voltage.
Parameter
SGT
Description
Setting
This signed value controls stallGuard2™ threshold ₀
level for stall output and sets the optimum
measurement range for readout. A lower value ^+1…
gives a higher sensitivity. Zero is the starting value ⁺⁶³
working with most motors. A higher value makes
stallGuard less sensitive and requires more torque
-1…-64
to indicate a stall.
Comment
indifferent value
less sensitivity
higher sensitivity
SFILT
SSPD
Status
word
SG
Enables the stallGuard2™ filter for more precision 0
of the measurement. If set, reduces the
measurement frequency to one measurement per
1
six fullsteps. In standard mode, a measurement is
taken each two fullsteps.
Selects the filtering for less noise at low motor 0
velocities.
1
Description
Range
standard mode
filtered mode
standard mode
low velocity mode
Comment
This is the stallGuard2™ result. A higher reading 0…
indicates less mechanical load. A lower reading 1023
indicates a higher load and thus a higher load
angle. Tune the SGT setting to show a SG reading
of 0 at maximum load before motor stall. This is
also signaled by the output SG_TST.
0: maximum load
low value: high load
high value: less load
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