Datasheet

TMC4671 Datasheet • IC Version V1.3 | Document Revision V2.00 • 2020-Apr-17

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6.3 Run Motor Open Loop

Initial turning a motor open loop is useful for determination of the association between phase voltage,

phase currents and for position sensor setup. Position sensors that are mounted on a motor might have

an opposite direction of rotation compared to the motor. The same direction of rotation is essential for

the FOC. In addition, the phase shift between rotor angle and angle that is measured by a position sensor

needs to be zero in best case. Otherwise the motor is operated at lower eﬃciency or turns in wrong

direction which causes instability.

6.3.1 Determination of Association between Phase Voltage and Phase Currents

For starters, the motor should be turned open loop to measure ADC oﬀsets and set ADC scaler oﬀset.

Additionally, the open loop turn is useful to validate (or to determine) the association between motor

phase currents and motor phase terminal voltages. This association is essential for the FOC. With proper

ADC channel selection setup, voltage U_UX1 is in phase with current I_UX1, voltage U_VX2 is in phase

with current I_VX2, and voltage U_WY1 is in phase with I_WY1. For two phase stepper motor, the voltage

U_Y2 is in phase with current I_Y2. Only two currents are measured and the other current is calculated by

TMC4671. For DC motor only one current is measured.

6.3.2 Determination of Direction of Rotation and Phase Shift of Angles

For absolute position sensors like Hall sensors, the phase shift an the direction of rotation only need to

be determined once initially. For relative position sensors, like incremental encoders, the direction of

turning needs to be determined everytime after power cycle. The relative orientation between measured

incremental encoder angle and rotor angle needs to be determined on each power-up.

6.4 Selection of Position Sensors

For closed loop operation, the type of encoder (digital hall, ABN encoder, analog Hall, SinCos) needs to

be set. For analog Hall signals or analog incremental encoders the user needs to adjust the analog ADC

channels for the analog encoders - similar to ADC oﬀset and ADC scaling as for current measuring ADC

channels. The TMC4671 allows the selection of diﬀerent types of position sensors for diﬀerent tasks. One

position sensor is for the inner FOC closed loop current control loop.

6.4.1 Selection of FOC sensor for PHI_E

One sensor needs to be selected for the FOC to measure the electrical angle PHI_E. This sensor is used for

the inner closed loop control loop for closed loop current control.

6.4.2 Selection of sensor for VELOCITY

One sensor needs to be selected for measurement of velocity. This can be the sensor selected for

measurement of PHI_E but it is more common to use the mechanical angle PHI_M for measurement of

velocity. Using electrical angles can give advantages for applications with slow motion for NPP more than

one because the minimum velocity in RPM [revolutions per minute] is one and the electrical angles have

higher speed than mechanical angles.

6.4.3 Selection of sensor for POSITION

One sensor needs to be selected for measurement of position of the rotor, the angle of the rotor. This can

be the sensor selected for measurement PHI_E but it is more usual to use the mechanical angle PHI_M for

measurement of position. For stepper motors it might make sense to select the electrical angle PHI_E for

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