Datasheet

TMC5041 DATASHEET (Rev. 1.13 / 2017-MAY-16) 40
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Velocity
Time
Stand still
PWM scale
PWM reaches
max. amplitude
255
0
Motor current
Nominal current
(sine wave RMS)
RMS current
constant
0
PWM scale
Current may drop due
to high velocity
Velocity
Time
Stand still
PWM scale
255
0
Motor current
Nominal current
(sine wave RMS)
0
PWM scale
PWM
_
GRAD too small
PWM
_GRAD ok
Current drops due to
too small PWM_GRAD
Current overshoots
due to too small
PWM_GRAD
PWM
_
GRAD ok
Setting for PWM_GRAD ok.
Setting for PWM_GRAD slightly too small.
Figure 7.4 Good and too small setting for PWM_GRAD
Be sure to use a symmetrical sense resistor layout and sense resistor traces of identical length and
well matching sense resistors for best performance.
Quick Start
For a quick start, see the Quick Configuration Guide in chapter 14.
7.2.1 Lower Current Limit
The autoscaling function imposes a lower limit for motor current regulation. As the coil current can
be measured in the shunt resistor during chopper on phase, only, a minimum chopper duty cycle
allowing coil current regulation is given by the blank time as set by TBL and by the chopper
frequency setting. Therefore, the motor specific minimum coil current in stealthChop autoscaling
mode rises with the supply voltage and the chopper frequency. A lower blanking time allows a lower
current limit. Extremely low currents (e.g. for standstill power down) can be realized with the non-
automatic current scaling or with the freewheeling option, only. The run current setting needs to be
kept above the lower limit: In case the PWM_SCALE drops to a too low value, e.g. because the current
scale was too low, the regulator may not be able to recover. The regulator will recover once the
motor is in standstill. The lower motor coil current limit can be calculated from motor parameters and
chopper settings:
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