Datasheet

TMC6200 DATASHEET (Rev. 1.04 / 2019-AUG-08) 29
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the resulting value as zero-reference. When changing amplification in the application, scale the offset
measured with a different amplification accordingly.
6.2.2 Thermal Drift
Further, the offset has a random certain thermal drift. Figure 6.5 shows an example. Thermal drift
especially concerns applications, where the IC heats up significantly during operation. Thermal
compensation therefore becomes necessary, when low motor currents have to be exactly measured in
a high current application, e.g. for field-oriented motor control. As the thermal drift basically shows a
linear dependence on the temperature, taking offset measurements at two temperature values will be
sufficient for linear interpolation and extrapolation of the actual offset. Therefore, board temperature
near the IC / near the power stage shall be measured. Compensation based on an initial testing
phase temperature curve per channel will be sufficient.
Example for offset compensation including thermal drift compensation:
1) Measure and compensate initial value at each power-up of the IC.
2) When the unit is powered up for the first time, store temperature and offset value for each channel
3) When the unit reaches a certain increased temperature for the first time (e.g. +40°C more than at
step 2), redo 1) and store temperature and offset values to EEPROM.
4) Use the results of steps 2) and 3) for compensating thermal drift during operation, by interpolating
between and extrapolating beyond the stored values
For applications with continuous motor operation, a floating mean value should be sufficient to
compensate for amplifier offset.
Figure 6.4 Random Output Offset at 20x amplification (Yellow: Output, Blue: VOFS input)