AMIS-30523 Datasheet, PDF (22/35 Pages) ON Semiconductor – CAN Micro-Stepping Motor Driver

AMIS−30523
Direction
The direction of rotation is selected by means of following
combination of the DIR input pin and the SPI−controlled
direction bit <DIRCTRL>. (see Table 15 SPI Control
Parameter Overview)
NXT input
Changes on the NXT input will move the motor current
one step up/down in the translator table (even when the
motor is disabled). Depending on the NXT−polarity bit
<NXTP> (see Table 15 SPI Control Parameter Overview),
the next step is initiated either on the rising edge or the
falling edge of the NXT input.
Translator Position
The translator position MSP[6:0] can be read in SPI Status
Register 3 (See Table 18 SPI Status Registers). This is a
7−bit number equivalent to the 1/32^th micro−step from
Table 12 “Circular Translator Table”. The translator
position is updated immediately following a NXT trigger.
Synchronization of Step Mode and NXT Input
When step mode is re−programmed to another resolution
(Figure 18), then this is put in effect immediately upon the
first arriving “NXT” input. If the micro−stepping resolution
is increased, the coil currents will be regulated to the nearest
micro−step, according to the fixed grid of the increased
resolution. If however the micro−stepping resolution is
decreased, then it is possible to introduce an offset (or phase
shift) in the micro−step translator table.
If the step resolution is decreased at a translator table
position that is shared both by the old and new resolution
setting, then the offset is zero and micro−stepping is
proceeds according to the translator table.
If the translator position is not shared both by the old and
new resolution setting, then the micro−stepping proceeds
with an offset relative to the translator table (See Figure 18
right hand side).
More information can be found in application note
AND8399/D.
NXT
Update
Translator Position
Update
Translator Position
Figure 17. Translator Position Timing Diagram
Change from lower to higher resolution
I_Y
DIR
I_Y
DIR
NXT2
NXT3
NXT1
endpos _NXT4
startpos
I_X
I_X
Change from higher to lower resolution
I_Y
DIR
endpos
I_Y
DIR
NXT1 _startpos
NXT2
I_{X NXT3}
I_X
Halfstep
1/4th Step
1/8th Step
Halfstep
Figure 18. 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]” (see Table 15 SPI Control Parameter
Overview). Whenever this parameter is changed, the
coil−currents will be updated immediately at the next PWM
period. Figure 19 presents the Peak−Current and Current
Ratings in conjunction to the Current setting CUR[4:0].
http://onsemi.com
22