8.3.4.1 External Reference

Use the external reference by applying the reference voltage to the designated reference input pins. The reference input pins are differential with positive and negative inputs. Program the reference multiplexer bits RMUXP[1:0] and RMUXN[1:0] to select the respective reference voltage for operation. For example, to select REFP0 and REFN0 as the reference voltage, program the REF register to the value of 0Ah. Follow the specified absolute and differential reference voltage operating conditions, as specified in the Recommended Operating Conditions.

Be aware of the reference input current when reference impedances are present, such as by the use of a resistor divider. Consider the effect of the resistance to system accuracy. Connect a capacitor across the reference input pins to filter noise. When R-C filters are used, match the time constants of the input signal filter to the reference voltage filter to maintain constant conversion noise over the signal operating range.