Datasheet

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

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4.5.4 ADC Selector & ADC Scaler w/ Oﬀset Correction

The ADC selector selects ADC channels for FOC. The 3-phase FOC uses two 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.

Info

Raw ADC values generally are of 16 bit width, regardless of their real resolution.

Info

The ADC scaler maps raw ADC values to the 16 bit signed (s16) range and centers

the values to zero by removing oﬀsets.

Figure 19: ADC Selector & Scaler w/ Oﬀset Correction

ADC oﬀsets and ADC scalers for the analog current measurement input channels need to be programmed

into the associated registers. Each ADC_I_U, ADC_I_V, ADC_I0_EXT, and ADC_I1_EXT are mapped either to

ADC_I0_RAW or to ADC_I1_RAW by ADC_I0_SELECT and ADC_I1_SELECT.

In addition, the ADC_OFFSET is for conversion of unsigned ADC values into signed ADC values as required

for the FOC. For FOC3, the third current

ADC_I2

is calculated via Kirchhoﬀ’s Law. This requires the correct

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