External reference is the default configuration on power-up or after device reset. An external reference voltage source can be connected to the REF pin with an appropriate decoupling capacitor placed between the REF and GND pins. Best SNR is achieved with a 5-V external reference because the internal reference is limited to 2.5 V. For improved thermal drift performance, a reference from the REF60xx family (REF6025, REF6030, REF6033, REF6041, REF6045, or REF6050) is recommended.