Datasheet

TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 38
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Hint
The values for PWM_OFS and PWM_GRAD can easily be optimized by tracing the motor current with a
current probe on the oscilloscope. Alternatively, automatic tuning determines these values and they
can be read out from PWM_OFS_AUTO and PWM_GRAD_AUTO.
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.
6.5 Flags in StealthChop
As StealthChop uses voltage mode driving, status flags based on current measurement respond
slower, respectively the driver reacts delayed to sudden changes of back EMF, like on a motor stall.
Attention
A motor stall, or abrupt stop of the motion during operation in StealthChop can trigger an
overcurrent condition. Depending on the previous motor velocity, and on the coil resistance of the
motor, it significantly increases motor current for a time of several 10ms. With low velocities, where
the back EMF is just a fraction of the supply voltage, there is no danger of triggering the short
detection. When homing using StallGuard4 to stop the motor upon stall, this is basically avoided.
6.5.1 Open Load Flags
In StealthChop mode, OLA and OLB show if the current regulation sees that the nominal current can
be reached on both coils.
- A flickering OLA or OLB can result from asymmetries in the sense resistors or in the motor
coils.
- An interrupted motor coil leads to a continuously active open load flag for the coil.
- One or both flags are active, if the current regulation did not succeed in scaling up to the full
target current within the last few fullsteps (because no motor is attached or a high velocity
exceeds the PWM limit).
With StealthChop, PWM_SCALE_SUM can be checked to detect the correct coil resistance.
UART