TMC2208 Datasheet, PDF (49/81 Pages) TRINAMIC Motion Control GmbH & Co. KG. – POWER DRIVER FOR STEPPER MOTORS

TMC220X, TMC222X DATASHEET (Rev. 1.02 / 2017-MAY-16)
49
Figure 7.2 No ledges in current wave with sufficient hysteresis (magenta: current A, yellow &
blue: sense resistor voltages A and B)
A too high hysteresis setting will lead to reduced chopper frequency and increased chopper noise but
will not yield any benefit for the wave shape.
Quick Start
For a quick start, see the Quick Configuration Guide in chapter 14.
For detail procedure see Application Note AN001 - Parameterization of spreadCycle
As experiments show, the setting is quite independent of the motor, because higher current motors
typically also have a lower coil resistance. Therefore choosing a low to medium default value for the
hysteresis (for example, effective hysteresis = 4) normally fits most applications. The setting can be
optimized by experimenting with the motor: A too low setting will result in reduced microstep
accuracy, while a too high setting will lead to more chopper noise and motor power dissipation.
When measuring the sense resistor voltage in motor standstill at a medium coil current with an
oscilloscope, a too low setting shows a fast decay phase not longer than the blanking time. When
the fast decay time becomes slightly longer than the blanking time, the setting is optimum. You can
reduce the off-time setting, if this is hard to reach.
The hysteresis principle could in some cases lead to the chopper frequency becoming too low, e.g.
when the coil resistance is high when compared to the supply voltage. This is avoided by splitting
the hysteresis setting into a start setting (HSTRT+HEND) and an end setting (HEND). An automatic
hysteresis decrementer (HDEC) interpolates between both settings, by decrementing the hysteresis
value stepwise each 16 system clocks. At the beginning of each chopper cycle, the hysteresis begins
with a value which is the sum of the start and the end values (HSTRT+HEND), and decrements during
the cycle, until either the chopper cycle ends or the hysteresis end value (HEND) is reached. This way,
the chopper frequency is stabilized at high amplitudes and low supply voltage situations, if the
frequency gets too low. This avoids the frequency reaching the audible range.
Hint
Highest motor velocities sometimes benefit from setting TOFF to 1 or 2 and a short TBL of 1 or 0.
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