Firstly,we want to know external reference input range. And we cannot find this
information on AD9288 datasheet, but we found this info(figure1),
We think the range of reference voltage in this table is for REFout, not for
REFin, right? And we also found in figure2, the input range can be adjusted
based on REFin, but what is their detailed relationship? For example, if we
input REFin=1.0 or 0.5V, what is the input range for single-end input?
The reference section of the datasheet refers to REFout, not REFin as you had
The input range adjustment tracks variations on REFin linearly (±5% of 1.25V).
Don’t exceed REFin by 1.25±5%.
REFin | Input Range
1.19V | 0.97V
1.25V | 1.0V
1.31V | 1.08V