Datasheet

TMC5160 DATASHEET (Rev. 1.01 / 2017-NOV-29) 57
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7.1 Automatic Tuning
stealthChop2 integrates an automatic tuning procedure (AT), which adapts the most important
operating parameters to the motor automatically. This way, stealthChop2 allows high motor dynamics
and supports powering down the motor to very low currents. Just two steps have to be respected by
the motion controller for best results: Start with the motor in standstill, but powered with nominal
run current (AT#1). Move the motor at a medium velocity, e.g. as part of a homing procedure (AT#2).
Figure 7.2 shows the tuning procedure.
Border conditions for AT#1 and AT#2 are shown in the following table:
AUTOMATIC TUNING TIMING AND BORDER CONDITIONS
Step
Parameter
Conditions
Required Duration
AT#1
PWM_
OFS_AUTO
- Motor in standstill and actual current scale (CS) is
identical to run current (IRUN).
- If standstill reduction is enabled, an initial step
pulse switches the drive back to run current, or set
IHOLD to IRUN.
- Pin VS at operating level.
Attention: Driver may reduce chopper frequency during
AT#1. Use reduced standstill current IHOLD<IRUN to
prevent extended periods of time at lower chopper
frequency
≤ 2^20+2*2^18 t
CLK
,
≤ 130ms
(with internal clock)
AT#2
PWM_
GRAD_AUTO
- Move motor at a velocity, where a significant
amount of back EMF is generated and where the full
run current can be reached. Conditions:
- 1.5 * PWM_OFS_AUTO < PWM_SCALE_SUM <
4 * PWM_OFS_AUTO
- PWM_SCALE_SUM < 255.
Hint: A typical range is 60-300 RPM.
8 fullsteps are required
for a change of +/-1.
For a typical motor with
PWM_GRAD_AUTO
optimum at 50 or less, up
to 400 fullsteps are
required when starting
from OTP default 0.
Determine best conditions for automatic tuning with the evaluation board.
Monitor PWM_SCALE_AUTO going down to zero during the constant velocity phase in AT#2 tuning. This
indicates a successful tuning.
Attention:
Operating in stealthChop without proper tuning can lead to high motor currents during a deceleration
ramp, especially with low resistive motors and fast deceleration settings. Follow the automatic tuning
process and check optimum tuning conditions using the evaluation board. It is recommended to use
an initial value for PWM_ settings determined per motor type.
Protect the power stage and supply by additionally tuning the overcurrent protection.