TMC262 DATASHEET (Rev. 2.07 / 2013-FEB-14)
9
4 stallGuard2 Load Measurement
stallGuard2 provides an accurate measurement of the load on the motor. It can be used for stall
detection as well as other uses at loads below those which stall the motor, such as coolStep load-
adaptive current reduction. (stallGuard2 is a more precise evolution of the earlier stallGuard
technology.)
The stallGuard2 measurement value changes linearly over a wide range of load, velocity, and current
settings, as shown in Figure 4.1. At maximum motor load, the value goes to zero or near to zero. This
corresponds to a load angle of 90° between the magnetic field of the coils and magnets in the rotor.
This also is the most energy-efficient point of operation for the motor.
1000
900
stallGuard2
Start value depends
on motor and
operating conditions
800
700
600
500
400
300
200
100
0
reading
stallGuard value reaches zero
and indicates danger of stall.
This point is set by stallGuard
threshold value SGT.
Motor stalls above this point.
Load angle exceeds 90° and
available torque sinks.
10
20
30
40
50
60
70
80
90 100
motor load
(% max. torque)
Figure 4.1 stallGuard2 load measurement SG as a function of load
Two parameters control stallGuard2 and one status value is returned.
Parameter
Description
Setting
Comment
SGT
7-bit signed integer that sets the stallGuard2 0
threshold level for asserting the SG_TST output
indifferent value
+1… +63
-1… -64
less sensitivity
and sets the optimum measurement range for
readout. Negative values increase sensitivity,
and positive values reduce sensitivity so more
torque is required to indicate a stall. Zero is a
good starting value. Operating at values below -
10 is not recommended.
higher sensitivity
SFILT
Mode bit which enables the stallGuard2 filter for 0
standard mode
filtered mode
more precision. If set, reduces the measurement
frequency to one measurement per four
fullsteps. If cleared, no filtering is performed.
1
Filtering
compensates
for
mechanical
asymmetries in the construction of the motor,
but at the expense of response time. Unfiltered
operation is recommended for rapid stall
detection. Filtered operation is recommended
for more precise load measurement.
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