TMC2100 DATASHEET (Rev. 1.07 / 2017-MAY-15)
19
Figure 5.4 Current regulation cannot follow during high acceleration phase
Hint
Operate the motor within your application when exploring stealthChop. Motor performance often is
better with a mechanical load, because it prevents the motor from stalling due mechanical oscillations
which can occur without load.
5.4 Switching between stealthChop and spreadCycle
It is principally possible to combine stealthChop and spreadCycle by toggling between two
configurations using the related CFG pins. But care must be taken to avoid operating in a wrong
microstepping mode. As the tristate detection logic needs a number of cycles to detect transition to
or from an open pin, the switching should only be done during standstill. Allow 3072 tCLK for
detection of the changed mode selection, before driving a new step. With internal clock, a 3ms delay
will ensure proper transition to the new mode, before the next step is done.
When enabling the stealthChop mode the first time using automatic current regulation, the motor
must be at stand still in order to allow a proper current regulation. When the drive switches to a
different chopper mode at a higher velocity, stealthChop logic stores the last current regulation
setting until the motor returns to a lower velocity again. This way, the regulation has a known
starting point when returning to a lower velocity, where stealthChop becomes re-enabled. Therefore,
neither the velocity threshold nor the supply voltage must be considerably changed during the phase
while the chopper is switched to a different mode, because otherwise the motor might lose steps or
the instantaneous current might be too high or too low.
Attention
A motor stall or a sudden change in the motor velocity may lead to the driver detecting a short
circuit, as the current can exceed the upper limit in these situations. In these situations, the automatic
current regulation may also reach a state of low current from which it cannot recover.
Stop motion, disable and re-enable the driver (using the ENN pin) and restart the motor from zero
velocity to recover from this situation.
Hint
Start the motor from standstill when switching on stealthChop the first time and keep it stopped for
at least 128 chopper periods to allow stealthChop to do initial standstill current control.
www.trinamic.com
TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
