TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.04 • 2018-Dec-11
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4.6.2 Stator Coil Currents I_X, I_Y and Association to Terminal Voltages U_X, U_Y
For two-phase motors (stepper) with four terminals X1, X2, and Y1, Y2, voltage U_Ux = U_X1 - U_X2 is in
phase with the measured current I_X and U_Wy = U_Y1 - U_Y2 is in phase with the measured current I_Y
according to equations (15) and (16) for FOC2.
UX (φe) = UX
UY (φe) = UY
∗
∗
sin(φe)
U_XY_FOC2
=
=
(15)
(16)
sin(φe + 90o)
IX (φe) = ID
IY (φe) = ID
∗
∗
sin(φe)
I_XY_FOC2
sin(φe + 90o)
4.6.3 ADC Selector & ADC Scaler w/ Offset Correction
The ADC selector selects ADC channels for FOC. The 3-phase FOC uses two of three ADC channels for
measurement and calculates the third channel via Kirchhoff’s Law using the scaled and offset-corrected
ADC values. The 2-phase FOC just uses two ADC channels because for a 2-phase stepper motor, the two
phases are independent from each other.
Note
The open-loop encoder is useful for setting up ADC channel selection, scaling,
and offset by running a motor open-loop.
The FOC23 Engine processes currents as 16 bit signed (s16) values. Raw ADC values are expanded to 16 bit
width, regardless of their resolution. With this, each ADC is available for read out as a 16 bit number.
The ADC scaler w/ offset correction is for the preprocessing of measured raw current values. It might be
used to map to user’s own units (e.g. A or mA). For scaling, gains of current amplifiers, reference voltages,
and offsets have to be taken into account.
Raw ADC values generally are of 16 bit width, regardless of their real resolution.
Info
Info
The ADC scaler maps raw ADC values to the 16 bit signed (s16) range and centers
the values to zero by removing offsets.
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