Datasheet

TMC262 / TMC262C DATASHEET (Rev. 2.22 / 2019-FEB-22) 37

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Figure 9.2 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 detail tuning 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. Choosing a medium default value for the hysteresis (for

example, effective HSTRT+HEND=10) 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, for

example when the coil resistance is high 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 these settings, by decrementing the hysteresis

value stepwise each 16, 32, 48, or 64 system clock cycles. 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.

target current

target current - hysteresis start

target current + hysteresis start

on sd fd sd

target current + hysteresis end

target current - hysteresis end

HDEC

Figure 9.3 SpreadCycle chopper mode showing the coil current during a chopper cycle