Datasheet
TMC2041 DATASHEET (Rev. 1.02 / 2017-MAY-16) 43
www.trinamic.com
10.1.1 Variable Velocity Limits
The SGT setting chosen as a result of the previously described SGT tuning can be used for a certain
velocity range. Outside this range, a stall may not be detected safely, and coolStep might not give the
optimum result.
back EMF reaches
supply voltage
optimum
SGT setting
Motor RPM
(200 FS motor)
stallGuard2
reading at
no load
2
4
6
8
10
12
14
16
100
200
300
400
500
600
700
800
900
1000
18
20
0 0 50 100 150 200 250 300 350 400 450 500 550 600
lower limit for stall
detection
good operation
range with single
SGT setting
Figure 10.2 Example: Optimum SGT setting and stallGuard2 reading with an example motor
In many applications, operation at or near a single operation point is used most of the time and a
single setting is sufficient.
In some applications, a velocity dependent tuning of the SGT value can be expedient, using a small
number of support points and linear interpolation.
10.1.2 Small Motors with High Torque Ripple and Resonance
Motors with a high detent torque show an increased variation of the stallGuard2 measurement value
SG with varying motor currents, especially at low currents. For these motors, the current dependency
should be checked for best result.
10.1.3 Temperature Dependence of Motor Coil Resistance
Motors working over a wide temperature range may require temperature correction, because motor
coil resistance increases with rising temperature. This can be corrected as a linear reduction of SG at
increasing temperature, as motor efficiency is reduced.
10.1.4 Accuracy and Reproducibility of stallGuard2 Measurement
In a production environment, it may be desirable to use a fixed SGT value within an application for
one motor type. Most of the unit-to-unit variation in stallGuard2 measurements results from manu-
facturing tolerances in motor construction. The measurement error of stallGuard2 – provided that all
other parameters remain stable – can be as low as: