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 VREF and VBIAS outputs of the REF20xx are generated from the same band-gap voltage as shown in the Functional Block Diagram 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 (max). The tracking accuracy increases to 6 ppm/°C (max) 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:
The tracking accuracy is as shown in Figure 48.