TMC262 DATASHEET (Rev. 2.07 / 2013-FEB-14)
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4.3 Detecting a Motor Stall
To safely detect a motor stall, a stall threshold must be determined using a specific SGT setting.
Therefore, you need to determine the maximum load the motor can drive without stalling and to
monitor the SG value at this load, for example some value within the range 0 to 400. The stall
threshold should be a value safely within the operating limits, to allow for parameter stray. So, your
microcontroller software should set a stall threshold which is slightly higher than the minimum value
seen before an actual motor stall occurs. The response at an SGT setting at or near 0 gives some idea
on the quality of the signal: Check the SG value without load and with maximum load. These values
should show a difference of at least 100 or a few 100, which shall be large compared to the offset. If
you set the SGT value so that a reading of 0 occurs at maximum motor load, an active high stall
output signal will be available at SG_TST output.
4.4 Limits of stallGuard2 Operation
stallGuard2 does not operate reliably at extreme motor velocities: Very low motor velocities (for many
motors, less than one revolution per second) generate a low back EMF and make the measurement
unstable and dependent on environment conditions (temperature, etc.). Other conditions will also lead
to extreme settings of SGT and poor response of the measurement value SG to the motor load.
Very high motor velocities, in which the full sinusoidal current is not driven into the motor coils also
lead to poor response. These velocities are typically characterized by the motor back EMF reaching the
supply voltage.
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