AMIS-30521_10 Datasheet, PDF (16/28 Pages) ON Semiconductor – Micro-Stepping Motor Driver

AMIS−30521, NCV70521
Change from lower to higher resolution
I_Y
DIR
endpos
I_Y
DIR
NXT3 ^NXT2
NXT1
NXT4
startpos
I_X
I_X
Change from higher to lower resolution
I_Y
endpos
DIR
NXT1
I_Y
startpos
DIR
NXT2
I_{X NXT3}
I_X
Halfstep
1/4^th step
1/8^th step
Halfstep
Figure 11. NXT−Step−Mode Synchronization
Left: change from lower to higher resolution. The left−hand side depicts the ending half−step position during which a new step mode res-
olution was programmed. The right−hand side diagram shows the effect of subsequent NXT commands on the micro−step position.
Right: change from higher to lower resolution. The left−hand side depicts the ending micro−step position during which a new step mode
resolution was programmed. The right−hand side diagram shows the effect of subsequent NXT commands on the half−step position.
NOTE: It is advised to reduce the micro−stepping resolution only at micro−step positions that overlap with desired micro−step positions
of the new resolution.
Programmable Peak−Current
The amplitude of the current waveform in the motor coils
(coil peak current = I_max) is adjusted by means of an SPI
parameter “CUR[4:0]” (Table 13). Whenever this
parameter is changed, the coil−currents will be updated
immediately at the next PWM period. Figure 12 presents the
Peak−Current and Current Ranges in conjunction to the
Current setting (CUR[4:0]).
Ipeak (CUR[4:0] = 11111)
Peak Current
Current Range 3
CUR = 23 −> 31
Ipeak (CUR[4:0] = 10110]
Current Range 2
CUR = 16 −> 22
Ipeak (CUR[4:0] = 01111)
Ipeak (CUR[4:0] = 01000)
0
Current Range 1
CUR = 9 −> 15
Current Range 0
CUR = 0 −> 8
8
15
22
31
Figure 12. Programmable Peak−Current Overview
CUR[4:0]
Speed and Load−Angle Output
The SLA−pin provides an output voltage that indicates the
level of the Back−e.m.f. voltage of the motor. This
Back−e.m.f. voltage is sampled during every so−called ”coil
current zero crossings”. Per coil, 2 zero−current positions
exist per electrical period, yielding in total 4 zero−current
observation points per electrical period.
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