TMC2225 DATASHEET (Rev. 1.15 / 2023-FEB-16)
47
I
target current + hysteresis start
target current + hysteresis end
target current
target current - hysteresis end
target current - hysteresis start
HDEC
on
sd
fd
sd
t
Figure 7.3 SpreadCycle chopper scheme showing coil current during a chopper cycle
These parameters control SpreadCycle mode:
Parameter
TOFF
TBL
HSTRT
HEND
Description
Setting
Sets the slow decay time (off time). This setting also 0
limits the maximum chopper frequency.
1…15
For operation with StealthChop, this parameter is not
used, but it is required to enable the motor. In case
of operation with StealthChop only, any setting is
OK.
Setting this parameter to zero completely disables all
driver transistors and the motor can free-wheel.
Comparator blank time. This time needs to safely 0
cover the switching event and the duration of the 1
ringing on the sense resistor. For most
applications, a setting of 1 or 2 is good. For highly 2
capacitive loads, a setting of 2 or 3 will be 3
required.
Hysteresis start setting. This value is an offset from 0…7
the hysteresis end value HEND.
Hysteresis end setting. Sets the hysteresis end value 0…2
after a number of decrements. The sum HSTRT+HEND 3
must be ≤16. At a current setting of max. 30
(amplitude reduced to 240), the sum is not limited. 4…15
Comment
chopper off
off time setting
NCLK= 24 + 32*TOFF
(1 will work with minimum
blank time of 24 clocks)
16 tCLK
24 tCLK
32 tCLK
40 tCLK
HSTRT=1…8
This value adds to HEND.
-3…-1: negative HEND
0: zero HEND
1…12: positive HEND
Even at HSTRT=0 and HEND=0, the TMC2225 sets a minimum hysteresis via analog circuitry.
EXAMPLE:
A hysteresis of 4 has been chosen. You might decide to not use hysteresis decrement. In this case
set:
HEND=6
HSTRT=0
(sets an effective end value of 6-3=3)
(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
HSTRT=6
(sets an effective end value of -3)
(sets an effective start value of hysteresis end +7: 7-3=4)
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