Datasheet

TMC5130A DATASHEET (Rev. 1.11 / 2015-OCT-08) 53
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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
However, the autoscaling function cannot measure low RMS current settings with high supply
voltages and low inductive motors, because chopper on time may become too short for successfully
measuring the motor current. Especially at higher PWM frequency settings the lower current limit
rises. This happens when the PWM on time required for reaching the necessary coil current falls
below the comparator blank time. Try a lower blanking time in order to reduce the 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. 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.
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 24.