TMC4330A Datasheet | Document Revision 1.01 • 2017-JAN-12
35/166
Start Velocity VSTART and Stop Velocity VSTOP
S-shaped and trapezoidal velocity ramps can be configured with unsigned start and stop
velocity values: VSTART, or VSTOP.
Per default, VSTART and VSTOP are set to 0. The sign is selected automatically,
depending on the current ramp status and the target velocity, or target position. This section
explains how to set up the respective values correctly.
Starting Ramps
with initial
Velocity
S-shaped and trapezoidal velocity ramps can be started with an initial velocity value,
if you set the VSTART value higher than zero (see Figure below).
In order to use trapezoidal ramps with an initial start velocity, do as follows:
Action:
Set RAMPMODE(1:0)=b’01 (register 0x20).
Set Trapezoidal ramp type accordingly, as explained before.
Set proper VSTART > 0 (register 0x25).
Set VSTOP = 0 (register 0x26).
Result:
The trapezoidal ramp starts with initial velocity.
NOTE:
The initial acceleration value is AMAX if VBREAK < VSTART, otherwise the starting
acceleration value is ASTART.
v(t)
A1L A1 A2 A3 A3L
VMAX
VBREAK
VSTART
t
Figure 22: Trapezoidal Ramp with initial Velocity
If trapezoidal ramp with initial velocity VSTART is selected:
Avoid unintended system behavior during positioning mode!
NOTICE
Use VSTART 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.
Turn page for information on how to configure S-shaped ramps with initial start
velocity.
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