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TMC4670 Datasheet PRELIMINARY • IC Version V0.99 | Document Revision V0.91 • 2016-Nov-09
– analog voltage input for motor temperature signal monitoring
Wrong scaling factors or wrong offsets might cause damages when the closed cur-
rent regulation is active. Integrated hardware limiters allow protection especially
in the setup phase when using carful limits.
Info
3.5.1 Internal ADC
The TMC4670 is equipped with internal ADCs with input voltage range of 0V . . . 2.5V for current measure-
ment, supply voltage measurement, analog hall signal measurement, analog encoder.
3.5.2 External ADC (LTC2351)
Alternatively to the integrated ADCs, the TMC4670 supports external SPI ADCs LTC2351 from Linear
Technology for current measurements. This is intended for current sensing on separate power stages.
3.5.2.1 ADC RAW
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.
3.5.2.2 ADC EXT
The user can write ADC values into the ADC EXT registers of the register bank from external ADC sources.
For example it there are high precision ADC values availbale from an external ADC.
3.5.3 ADC Selector & ADC Scaler w/ Offset Correction
The ADC selector selects ADC channles for FOC. The 3-phase FOC used two of three ADC channles for
measurement and calculates the third channel via Kirchhoff’s Law from the scaled an offset corrected
ADC values. The 2-phase FOC just used two ADC channels because for the 2-phase stepper motor the two
phases are independent from each other.
Note
The Open Loop Encoder is useful for setup of ADC channel selection, scaling, and
offset by turning a motor open loop.
The FOC23 Engine processes currents as 16 bit signed (s16) values. Raw ADC values are expanded to 16 bit
width independent of their resolution. With this, each ADC is available for read out a a 16 bit number.
The ADC scaler w/ offset correction is for pre-processing of measured raw current values. It might be used
to map to own units (e.g. A or mA). For scaling, gains of current amplifiers, reference voltages, and offsets
have to be takin into account.
Raw ADC values generally are of 16 bit width independent of their real resolution.
Info
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