TMC5160 DATASHEET (Rev. 1.08 / 2018-NOV-19)
88
13.1.1 Variable Velocity Limits TCOOLTHRS and THIGH
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.
good operation
range with single
1000
900
800
700
600
500
400
300
200
100
0
20
18
16
14
12
10
8
SGT setting
stallGuard2
reading at
no load
optimum
SGT setting
6
4
2
0
50
100
150
200
250
300
350
400
450
500
550
600
Motor RPM
(200 FS motor)
lower limit for stall
detection
back EMF reaches
supply voltage
Figure 13.2 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. The driver provides a lower and an upper velocity threshold to match this.
The stall detection is disabled outside the determined operation point, e.g. during acceleration phases
preceding a sensorless homing procedure when setting TCOOLTHRS to a matching value. An upper
limit can be specified by THIGH.
In some applications, a velocity dependent tuning of the SGT value can be expedient, using a small
number of support points and linear interpolation.
13.1.2 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.
13.1.3 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 SGT at
increasing temperature, as motor efficiency is reduced.
13.1.4 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:
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