Most single-supply systems require an additional stable voltage in the middle of the analog-to-digital converter (ADC) input range to bias input bipolar signals. The V_REF and V_BIAS outputs of the REF20xx are generated from the same band-gap voltage as shown in the Section 9.2 section. Hence, both outputs track each other over the full temperature range of –40°C to 125°C with an accuracy of 7 ppm/°C (maximum). The tracking accuracy increases to 6 ppm/°C (maximum) when the temperature range is limited to –40°C to 85°C. The tracking error is calculated using the box method, as described by Equation 2:

Equation 2.

where

The tracking accuracy is as shown in Figure 9-1.

Figure 9-1 V_REF and V_BIAS Tracking vs Temperature