Datasheet

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

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scaling and oﬀset correction beforehand. For FOC2, there is no calculation of a third current. The scaling

factors ADC_I0_SCALE and ADC_I1_SCALE are displayed in a Q8.8 format which results in the following

equations:

ADC_I0 = (ADC_I0_RAW − ADC_I0_OFFSET) · ADC_I0_SCALE / 256 (24)

ADC_I1 = (ADC_I1_RAW − ADC_I1_OFFSET) · ADC_I1_SCALE / 256 (25)

The ADC_UX_SELECT selects one of the three ADC channels ADC_I0, ADC_I1, or ADC_I2 for ADC_UX.

The ADC_V_SELECT selects one of the three ADC channels ADC_I0, ADC_I1, or ADC_I2 for ADC_V.

The ADC_WY_SELECT selects one of the three ADC channels ADC_I0, ADC_I1, or ADC_I2 for ADC_WY.

The ADC_UX, ADC_V, and ADC_WY are for the FOC3 (U, V, W).

The ADC_UX and ADC_WY (X, Y) are for the FOC2 (UX, WY).

Note

The open-loop encoder is useful to run a motor open loop for setting up the ADC

channel selection with correct association between phase currents I_U, I_V, I_W

and phase voltages U_U, U_V, U_W.

4.6 Encoder Engine

The encoder engine is an uniﬁed position sensor interface. It maps the selected encoder position informa-

tion to electrical position (phi_e) and to mechanical position (phi_m). Both are 16 bit values. The encoder

engine maps single turn positions from position sensors to multi-turn positions. The user can overwrite

the multi-turn position for initialization.

The diﬀerent position sensors are the position sources for torque and ﬂux control via FOC, for velocity

control, and for position control. The PHI_E_SELECTION selects the source of the electrical angle phi_e

for the inner FOC control loop. VELOCITY_SELECTION selects the source for velocity measurement. With

phi_e selected as source for velocity measurement, one gets the electrical velocity. With the mechanical

angle phi_m selected as source for velocity measurement, one gets the mechanical velocity taking the

set number of pole pairs (N_POLE_PAIRS) of the motor into account. Nevertheless, for a highly precise

positioning, it might be useful to do positioning based on the electrical angle phi_e.

4.6.1 Open-Loop Encoder

For initial system setup, the encoder engine is equipped with an open-loop position generator. This allows

for turning the motor open-loop by specifying speed in rpm and acceleration in rpm/s, together with

a voltage UD_EXT in D direction. As such, the open-loop encoder is not a real encoder. It simply gives

positions as an encoder does. The open-loop decoder has a direction bit to deﬁne direction of motion for

the application.

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