Datasheet

TMC2209 DATASHEET (Rev. 1.03 / 2019-JUN-26) 55
www.trinamic.com
11 StallGuard4 Load Measurement
StallGuard4 provides an accurate measurement of the load on the motor. It is developed for operation
in conjunction with StealthChop. StallGuard 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. The
StallGuard4 measurement value changes linearly over a wide range of load, velocity, and current
settings, as shown in Figure 11.1. When approaching maximum motor load, the value goes down to a
motor-specific lower value. 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.
motor load
(% max. torque)
StallGuard4 reading
SG_RESULT
50
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70 80 90 100
Start value depends
on motor, velocity
and operating current
Motor stalls above this point.
Load angle exceeds 90° and
available torque sinks.
SG_RESULT reaches compare
value and indicates danger of
stall. This point is set by
stallGuard threshold value
SGTHRS.
Stall detection
threshold SGTHRS*2
100% load value depends on
motor, operating current and
velocity
Stall Output
high
low
Figure 11.1 Function principle of StallGuard4
Parameter
Description
Setting
Comment
SGTHRS
This value controls the StallGuard4 threshold
level for stall detection. It compensates for
motor specific characteristics and controls
sensitivity. A higher value gives a higher
sensitivity. A higher value makes StallGuard4
more sensitive and requires less torque to
indicate a stall.
0… 255
The double of this value is
compared to SG_RESULT.
The stall output becomes
active if SG_RESULT fall
below this value.
Status word
Description
Range
Comment
SG_RESULT
This is the StallGuard4 result. A higher reading
indicates less mechanical load. A lower reading
indicates a higher load and thus a higher load
angle.
0… 510
Low value: highest load
High value: high load
In order to use StallGuard4, check the sensitivity of the motor at border conditions.
11.1 StallGuard4 vs. StallGuard2
StallGuard4 is optimized for operation with StealthChop, its predecessor StallGuard2 works with
SpreadCycle. The function is similar: Both deliver a load value, going from a high value at low load, to
a low value at high load. While StallGuard2 becomes tuned to show a “0”-reading for stall detection,
StallGuard4 uses a comparison-value to trigger stall detection, rather than shifting SG_RESULT itself.
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