SBAS661C February 2015 – May 2021 ADS1262 , ADS1263
The ADC provides three external reference inputs. The reference inputs are differential with independent positive and negative inputs. The reference inputs are the analog pins, AIN0 to AIN5. Typically, the positive reference is applied to pin AIN0, AIN2, or AIN4, and the negative reference is applied to pin AIN1, AIN2, or AIN3. The reference polarity can be negative, but the ADC requires a positive voltage reference. In this case, reverse the polarity using the internal polarity-reversal switch (ADC1 reference only). The reference polarity-reversal switch changes the reference polarity from negative to positive, and is controlled by REFREV (bit 7 of MODE0).
The reference inputs are high impedance. A reference input current flowing through a reference-voltage source impedance leads to possible loading errors (see Figure 7-34). To reduce the input current, use an external reference buffer; however, in most applications, an external reference buffer is not necessary.
Connect a 100-nF bypass capacitor across the external reference input pins. Follow the specified absolute and differential reference voltage requirements.