What analogue input voltages does this ADC understand?
From what I can understand from the datasheet, the input voltage can be defined from 1V p-p to 2V p-p

Span = 2 × (REFT − REFB) = 2 × VREF   --  (From page 17)

VREF = 0.5 × (1 + R2/R1)   --  (From pages 20/21)