Datasheet

TMC4361A Datasheet | Document Revision 1.22 • 2017-JAN-12
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Read entire documentation; especially the “Supplemental Directives” on page 224.
 MAIN MANUAL 
For some S-shaped ramp applications it can be useful to start with a defined velocity
value ( VSTART > 0);but not with the maximum acceleration value AMAX .
In order to start with a defined velocity value, do as follows:
Action:
 Set RAMPMODE (1:0) =b’10 (register 0x20).
 Set S-shaped ramp type accordingly, as explained before.
 Set proper VSTART > 0 (register 0x25).
 Set proper VSTOP > 0 (register 0x26).
 Set use_astart_and_vstart =1 (bit0 of the GENERAL_CONF register 0x00).
Result :
The following special ramp types can be generated in this way, as shown below.
i Section B1 is passed through although VSTART is used.
Using VSTART and starting acceleration of 0
for S-shaped ramps
Using VSTART and starting acceleration,
which is smaller than AMAX for S-shaped ramps
Figure 28: S-shaped Ramps with combined VSTART and ASTART Parameters
If S-shaped ramp with VSTART , ASTART , and VSTOP is selected:
Avoid unintended system behavior during positioning mode!
 Keep in mind that the S-shaped character of the curve is maintained. Because
ASTART is the start acceleration value, the ramp will always execute phase B2,
which could result in positioning overshoots.
 Use VSTART and ASTART > 0 without setting VSTOP > VSTART only in
positioning mode, if there is enough distance between the current position
XACTUAL and the target position XTARGET .
This will ensure smooth operation during positioning mode.
v(t)
VMAX
B
1
B
12
B
23
B
34
B
3
B
4
B
2
VSTOP
VSTART
a
START
= 0
v(t)
t
VMAX
B
1
B
12
B
23
B
34
B
3
B
4
B
2
VSTOP
VSTART
a
START
> 0
Combined Use of
VSTART and
ASTART for
S-shaped Ramps
NOTICE