Offset error is the deviation from the ideal output with zero input current and most often limits measurement accuracy at low input current levels. Offset error can be referred to the output as offset voltage error or referred to the input as offset current error. When divided by device sensitivity, S, output voltage offset error V_OE is input referred as input current offset error I_OS (see Equation 4). Offset error referred to the input (RTI) allows for more direct comparisons or offset error with input current. Regardless of whether offset error is referred to the input as current offset error I_OS, or to the output as voltage offset error V_OE, offset error is a single error source and should only be included once in either input referred, or output referred error calculations.

As shown in Figure 7-1, the output voltage offset error V_OE of the TMCS1126 is the difference between the zero current output voltage V_OUT,0A and the zero current output reference voltage V_REF (see Equation 5).

The output offset error V_OE includes magnetic offset error in the Hall sensor, offset voltage error in the signal chain, and offset error in the internal zero current output reference voltage V_REF. The internal zero current output reference voltage is brought out to pin VREF so that errors in the internal reference voltage as well as errors introduced at the system level can be removed.

Offset drift is the change in the offset as a function of temperature T. Output offset drift is reported in µV/°C. To calculate offset error at any given temperature, multiply the offset drift by the change in temperature and add it to offset error at 25°C (see Equation 6).

where

• V_OE,drift is the output voltage offset drift with temperature in µV/°C.
• ΔT is the change in device temperature from 25°C.