How long does it take the AD7722 to settle after a step change on the input?
The time required for the AD7722 to settle after a step change in the input is
84 samples (5376 CLKIN cycles). You must wait 128 samples (8192 CLKIN cycles)
after a power-on condition, a RESET or a sync operation; the extra time is
required to get the modulator into a known state and flush the digital filter.
Therefore during the initialization routine it is necessary to discard 128
samples. You only need to do this once provided you do not perform a reset or
FSIN operation. Thereafter discard 84 samples after a step change in the input.