TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.04 • 2018-Dec-11
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4.7.9.3 External Position Register
A register value written into the register bank via the application interface is available for commutation
as well. With this, the user can interface to any encoder by just writing positions extracted from external
encoder into this regulator. From the decoder engine point of view this is just one more selectable encoder
source.
4.7.10 Encoder Initialization Support
The TMC4671 needs proper feedback for correct and stable operation. One main parameter is the com-
mutation angle offset PHI_E_OFFSET. This offset must not be calculated when an absolute sensor system
like analog or digital Hall sensors is used. All other supported feedback systems need to be initialized -
their PHI_E_OFFSETs need to be identified. The user has several options to determine PHI_E_OFFSET with
support of the TMC4671.
4.7.10.1 Encoder Initialization in Open-Loop Mode
In the case of a free driving motor, the motor can be switched to Open-Loop Mode. In this mode, the
used commutation angle (PHI_OPEN_LOOP) can be used to match the measured PHI_E. This method is
supported by the TMCL-IDE.
4.7.10.2 Encoder Initialization by Minimal Movement
If the motor shall not make a big move during initialization, the MOTION_MODE ENCODER_INIT_MINI_MOVE
can be used which determines PHI_E_OFFSET by ramping up the flux and controlling the movement to
a minimum by manipulating the used PHI_E_OFFSET. After the procedure is finished, the estimated
PHI_E_OFFSET can be read from the register and used as the corresponding PHI_E_OFFSET for the feedback
system.
Figure 22: Encoder Initialization by minimal Movement
The flux ramping can be controlled by setting the U_D_INKR - which manipulates the slope of the ramp.
The maximum voltage can be set by the parameter U_D_MAX. During operation, the current is monitored
and the process is stopped when the current limit I_D_MAX is reached.
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