AMIS30512C5122G Datasheet, PDF (11/30 Pages) ON Semiconductor – Micro-Stepping Motor Driver

AMIS−30512
Icoil
Duty Cycle
< 50%
Duty Cycle > 50%
Actual value
Duty Cycle < 50%
Set value
t
TPWM
Figure 8. Automatic Duty Cycle Adaptation
Step Translator
Step Mode
The step translator provides the control of the motor by
means of SPI register Stepmode: SM[2:0], SPI register
DIRCNTRL, and input pins DIR and NXT. It is translating
consecutive steps in corresponding currents in both motor
coils for a given step mode.
One out of seven possible stepping modes can be selected
through SPI−bits SM[2:0] (Table 26: SPI Control Parameter
Overview SM[2:0]) After power−on or hard reset, the
coil−current translator is set to the default 1/32
micro−stepping at position ‘0’. Upon changing the step
mode, the translator jumps to position 0* of the
corresponding stepping mode. When remaining in the same
step mode, subsequent translator positions are all in the same
column and increased or decreased with 1. Table 9 lists the
output current versus the translator position.
As shown in Figure 9 the output current−pairs can be
projected approximately on a circle in the (I_x,I_y) plane.
There is, however, one exception: uncompensated half step.
In this step mode the currents are not regulated to a fraction
of Imax but are in all intermediate steps regulated at 100
percent. In the (I_x,I_y) plane the current−pairs are projected
on a square. Table 8 lists the output current versus the
translator position for this case.
Table 8. Square Translator Table for Full Step and Uncompensated Half Step
Stepmode ( SM[2:0] )
101
110
MSP[6:0]
Uncompensated Half−Step
Full Step
000 0000
0*
−
001 0000
1
1
010 0000
2
−
011 0000
3
2
100 0000
4
−
101 0000
5
3
110 0000
6
−
111 0000
7
0*
% of Imax
Coil x
0
100
100
100
0
−100
−100
−100
Coil y
100
100
0
−100
−100
−100
0
100
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