On page 29 of the datasheet, the equation doesn't show any dependency, but when we toggle the Rext bit in the control register the output current varies even though the DAC count is constant.
The DC specifications shown on page 6 of the AD5422 data sheet are for both an ideal external value of Rset and the internal Rset. So the output current may change when you toggle between the External Rset and internal Rset but the part will still be within the accuracy specifications.
If you are observing a value greater that this it is likely that you are sequencing the commands in the control register incorrectly. See description of REXT on page 30 of the data sheet for further information.
Michael (PDA Applications)
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