Datasheet

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

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4.4.7 ADC RAW values

The sampled raw ADC values are available for read out by the user. This is important during the system

setup phase to determine oﬀset and scaling factors.

4.4.8 ADC_SCALE and ADC_OFFSET

The FOC engine expects oﬀset corrected ADC current values, scaled into the FOC engine’s 16 bit (s16) ﬁxed

point representation. The integrated scaler and oﬀset compensator maps raw ADC samples of current

measurement channels to 16 bit two’s complement values (s16). While the oﬀset is compensated by

subtraction, the oﬀset is represented as an unsigned value. The scaling value is signed to compensate

wrong measurement direction. The s16 scaled ADC values are available for read out from the register

(ADC_I1, ADC_I0) resp. (AENC_UX, AENC_VN, AENC_WY) by the user.

Info

Wrong scaling factors (ADC_SCALE) or wrong oﬀsets (ADC_OFFSET) might cause

damages when the FOC is active. Integrated hardware limiters allow protection -

especially in the setup phase when using careful limits.

4.4.9 ADC Gain Factors for Real World Values

Each ADC channel of the TMC4671 has an individual gain factor determined by its associated chain of gain

factors and by digital scaling factors if available for an ADC channel. ADC register values are either 16 bit

unsigned vaulues (u16) or 16 bit signed vaules (s16). With gain factors one can calculate ADC values as real

world values if required.

Gain factors IgainADC for ADC current values are typical in units [A/LSB] or [mA/LSB]. Gain factors UgainADC

for ADC voltage values are typical in units [V/LSB] or [mV/LSB].

ADCmeasuredCurrent[A] = IgainADC[A/LSB] * ADC_CURRENT_S16 (7)

ADCmeasuredVoltage[V] = UgainADC[V/LSB] * ADC_VOLTAGE_S16 (8)

ADCmeasuredVoltage[V] = UgainADC[V/LSB] * ADC_VOLTAGE_U16 (9)

4.4.10 Internal Delta Sigma ADCs

The TMC4671 is equipped with internal delta sigma ADCs for current measurement, supply voltage

measurement, analog GPIs and analog encoder signal measurement. Delta sigma ADCs, as integrated

within the TMC4671, together with programmable digital ﬁlters are ﬂexible in parameterizing concerning

resolution vs. speed. The advantage of delta sigma ADCs is that the user can adjust measurement from

lower speed with higher resolution to higher speed with lower resolution. This ﬁts with motor control

application. Higher resolution is required for low speed signals, while lower resolution satisﬁes the needs

for high speed signals.

Due to high oversampling, the analog input front-end is easier to implement than for successive approxi-

mation register ADCs as anti aliasing ﬁlters can be chosen to a much higher cutoﬀ frequency. The ADC

Engine processes all ADC channels in parallel hardware - avoiding phase shifts between the channels

compared to ADC channels integrated in MCUs.

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