AMIS-30521_10 Datasheet, PDF (12/28 Pages) ON Semiconductor – Micro-Stepping Motor Driver

AMIS−30521, NCV70521
Step Translator and 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 stepmode.
One out of 7 possible stepping modes can be selected
through SPI−bits SM[2:0] (Table 12).
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 10 lists the output current vs. 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 are however two exceptions: uncompensated half step
and full step. In these stepmodes the two currents are not
regulated to a fraction of I_max but are in all intermediate steps
regulated at 100%. In the (I_x,I_y) plane the current−pairs are
projected on a square. Table 9 list the output current vs. the
translator position for these cases.
Table 9. SQUARE TRANSLATOR TABLE FOR FULL STEP AND UNCOMPENSATED HALF STEP
Stepmode ( SM[2:0] )
101
110
% of I_max
MSP[6:0]
Uncompensated Half−Step
Full−Step
Coil x
000 0000
0*
−
0
001 0000
1
1
100
010 0000
2
−
100
011 0000
3
2
100
100 0000
4
−
0
101 0000
5
3
−100
110 0000
6
−
−100
111 0000
7
0
−100
Coil y
100
100
0
−100
−100
−100
0
100
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