Datasheet

TMC5041 DATASHEET (Rev. 1.13 / 2017-MAY-16) 45
www.trinamic.com
7.6 Freewheeling and Passive Motor Braking
stealthChop provides different options for motor standstill. These options can be enabled by setting
the standstill current IHOLD to zero and choosing the desired option using the FREEWHEEL setting.
The desired option becomes enabled after a time period specified by TZEROWAIT and IHOLD_DELAY.
The PWM_SCALE regulation becomes frozen once the motor target current is at zero current in order
to ensure a quick startup.
Parameter
Description
Setting
Comment
VCOOLTHRS
VHIGH
Whichever is lower, specifies the upper velocity
for operation in stealthChop voltage PWM mode.
0 …
2^23-1
pwm_
autoscale
Enable automatic current scaling using current
measurement or use fixed scaling mode.
0
Fixed mode
1
Automatic scaling with
current regulator
PWM_FREQ
PWM frequency selection. stealthChop uses a fixed
PWM frequency by dividing the system clock
frequency using a programmable divider. Use the
lowest setting giving good results.
0
f
PWM
=2/1024 f
CLK
1
f
PWM
=2/683 f
CLK
2
f
PWM
=2/512 f
CLK
3
f
PWM
=2/410 f
CLK
PWM_GRAD
Global enable and
regulation loop gradient when pwm_autoscale=1.
0
Do not use stealthChop
1 … 15
stealthChop enabled
PWM_AMPL
User defined PWM amplitude for fixed scaling or
amplitude limit for re-entry into stealthChop mode
when pwm_autoscale=1.
0 … 255
FREEWHEEL
Stand still option when motor current setting is
zero (I_HOLD=0). Only available with stealthChop
enabled. The freewheeling option makes the
motor easy movable, while both coil short options
realize a passive brake. Mode 2 will brake more
intensely than mode 3, because low side drivers
(LS) have lower resistance than high side drivers.
0
Normal operation
1
Freewheeling
2
Coil shorted using LS
drivers
3
Coil shorted using HS
drivers
PWM_SCALE
Read back of the actual stealthChop voltage PWM
scaling as determined by the current regulation.
Can be used to detect motor load and stall when
autoscale=1.
0 … 255
(read
only)
The scaling value
becomes frozen when
operating in a different
chopper mode
TOFF
General enable for the motor driver, the actual
value does not influence stealthChop
0
Driver off
1 … 15
Driver enabled
TBL
Selects the comparator blank time. This time needs to
safely cover the switching event and the duration of the
ringing on the sense resistor. For most applications, a
setting of 1 or 2 is good. For highly capacitive loads,
e.g. when filter networks are used, a setting of 2 or 3
will be required. A lower setting allows stealthChop to
regulate down to lower coil current values.
0
16 t
CLK
1
24 t
CLK
2
36 t
CLK
3
54 t
CLK
IRUN
IHOLD
Run and hold current setting for stealth Chop
operation – only used with pwm_autoscale=1
See chapter on current
setting for details