SBAS991 February 2021 ADC3663
The ADC voltage reference can be selected using the REFBUF pin. Even though there is an internal 100 kΩ pull-up resistor to AVDD, the REFBUF pin should be set to a voltage externally and not left floating. When using a voltage divider to set the REFBUF voltage (R1 and R2 in Figure 8-41), resistor values < 5 kΩ should be used.
|REFBUF VOLTAGE||VOLTAGE REFERENCE OPTION||CLOCKING OPTION|
|> 1.7 V (Default)||External reference||Differential clock input|
|1.2 V (1.15-1.25V)||External 1.2V input on REFBUF pin using internal gain buffer||Differential clock input|
|0.5 - 0.7V||Internal reference||Differential clock input|
|< 0.1V||Internal reference||Single ended clock input|