The internal reference can be disabled by simply applying an external reference voltage into the EXTIO pin, which in this case functions as an input. The use of an external reference may be considered for applications that require higher accuracy and drift performance or to add the ability of dynamic gain control.

While a 0.1-µF capacitor is recommended to be used with the internal reference, it is optional for the external reference operation. The reference input, EXTIO, has a high input impedance (1 MΩ) and can easily be driven by various sources. Note that the voltage range of the external reference must stay within the compliance range of the reference input.