USB-2-RTMI datasheet(10/157 Pages) TRINAMIC

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TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.04 • 2018-Dec-11

10 / 157

3.5.1 Coordinate Transformations - Clarke, Park, iClarke, iPark

The FOC requires diﬀerent coordinate transformations formulated as a set of matrix multiplications. These

are the Clarke Transformation (Clarke), the Park Transformation (Park), the inverse Park Transforma-

tion (iPark) and the inverse Clarke Transformation (iClarke). Some put Park and Clarke together as DQ

transformation and Park and Clarke as inverse DQ transformation.

The TMC4671 takes care of the required transformations so the user no longer has to

ght with implemen-

tation details of these transformations.

3.5.2 Measurement of Stator Coil Currents

The measurement of the stator coil currents is required for the FOC to calculate a magnetic axis out of the

stator

eld caused by the currents

owing through the stator coils.

Coil current stands for motor torque in context of FOC. This is because motor torque is proportional

to motor current, de ned by the torque constant of a motor. In addition, the torque depends on the

orientation of the rotor of the motor relative to the magnetic

eld produced by the current through the

coils of the stator of the motor.

3.5.3 Stator Coil Currents I_U, I_V, I_W and Association to Terminal Voltages U_U, U_V, U_W

The correct association between stator terminal voltages U_U, U_V, U_W and stator coil currents I_U, I_V,

I_W is essential for the FOC. In addition to the association, the signs of each current channel need to

t. Signs of the current can be adapted numerically by the ADC scaler. The mapping of ADC channels is

programmable via con guration registers for the ADC selector. Initial setup is supported by the integrated

open loop encoder block, that can support the user to turn a motor open loop.

3.5.3.1 Chain of Gains for ADC Raw Values

An ADC raw value is a result of a chain of gains that determine it. A coil current I_SENSE

owing through a

sense resistor causes a voltage diﬀerence according to Ohm’s law. The resulting ADC raw value is a result

of the analog signal path according to

ADC_RAW = (I_SENSE ∗ ADC_GAIN) + ADC_OFFSET.

(1)

The ADC_GAIN is a result of a chain of gains with individual signs. The sign of the ADC_GAIN is positive

or negative, depending on the association of connections between sense ampli er inputs and the sense

resistor terminals. The ADC_OFFSET is the result of electrical oﬀsets of the phase current measurement

signal path. For the TMC4671, the maximum ADC_RAW value ADC_RAW_MAX = (216 − 1) and the minimum

ADC raw value is ADC_RAW_MIN = 0.

ADC_GAIN

(

I_SENSE_MAX

∗ R_SENSE

)

∗

SENSE_AMPLIFIER_GAIN

∗

(

ADC_RAW_MAX/ADC_U_MAX

)

(2)

For the FOC, the ADC_RAW is scaled by the ADC scaler of the TMC4671 together with subtraction of oﬀset

to compensate it. Internally, the TMC4671 FOC engine calculates with s16 values. Thus, the ADC scaling

needs to be chosen so that the measured currents

t into the s16 range. With the ADC scaler, the user can

choose a scaling with physical units like [mA].

Terms of delivery and rights to technical change reserved.

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