AMIS-30511 Datasheet, PDF (14/28 Pages) ON Semiconductor – Micro-Stepping Motor Driver

AMIS−30511
I_y
I_y
I_y
Start = 0
Step 1
Step 2
Step 3
I_x
Start = 0
Step 1
Start = 0
Step 2
I_x
Step 1
I_x
1/4^th micro step
SM[2:0] = 011
Step 3
Uncompensated Half Step
SM[2:0] = 101
Step 3
Step 2
Full Step
SM[2:0] = 110
Figure 7. Translator Table: Circular and Square
Direction
The direction of rotation is selected by means of following
combination of the DIR input pin and the SPI−controlled
direction bit <DIRCTRL>. (Table 12: SPI Control Register 1)
NXT Input
Changes on the NXT input will move the motor current
one step up/down in the translator table. Depending on the
NXT−polarity bit <NXTP> (Table 12: SPI Control Register
1), the next step is initiated either on the rising edge or the
falling edge of the NXT input.
Translator Position
The translator position can be read in Table 28: SPI Status
Register 3. This is a 7−bit number equivalent to the 1/32th
micro−step from Table 9: Circular Translator Table. The
translator position is updated immediately following a NXT
trigger.
NXT
Update
Translator Position
Update
Translator Position
Figure 8. Translator Position Timing Diagram
Synchronization of Step Mode and NXT Input
When step mode is re−programmed to another resolution
(Table 11: SPI Control Register 0), then this is put in effect
immediately upon the first arriving “NXT” input. If the
micro−stepping resolution is increased (see Figure 9) then
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 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 8
right hand side).
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