Datasheet

TMC2041 DATASHEET (Rev. 1.02 / 2017-MAY-16) 37
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I
target current
target current - hysteresis start
target current + hysteresis start
on sd fd sd
target current + hysteresis end
target current - hysteresis end
HDEC
Figure 8.3 spreadCycle chopper scheme showing coil current during a chopper cycle
Two parameters control spreadCycle mode:
Parameter
Description
Setting
Comment
HSTRT
Hysteresis start setting. This value is an offset
from the hysteresis end value HEND.
0…7
HSTRT=1…8
This value adds to HEND.
HEND
Hysteresis end setting. Sets the hysteresis end
value after a number of decrements. The sum
HSTRT+HEND must be ≤16. At a current setting of
max. 30 (amplitude reduced to 240), the sum is
not limited.
0…2
-3…-1: negative HEND
3
0: zero HEND
4…15
1…12: positive HEND
Even at HSTRT=0 and HEND=0, the TMC2041 sets a minimum hysteresis via analog circuitry.
Example:
In the example a hysteresis of 4 has been chosen. You might decide to not use hysteresis
decrement. In this case set:
HEND=6 (sets an effective end value of 6-3=3)
HSTRT=0 (sets minimum hysteresis, i.e. 1: 3+1=4)
In order to take advantage of the variable hysteresis, we can set most of the value to the
HSTRT, i.e. 4, and the remaining 1 to hysteresis end. The resulting configuration register values
are as follows:
HEND=0 (sets an effective end value of -3)
HSTRT=6 (sets an effective start value of hysteresis end +7: 7-3=4)
Hint
Highest motor velocities sometimes benefit from setting TOFF to 1, 2 or 3 and a short TBL of 1 or 0.