AD2S80A: Output is not linear, 2-3 degrees phase difference between sine and cosine input,

Q

R/D-converter's output is not linear (0-2degrees of non-linearity): There is a
small phase shift of 2-3 degrees phase difference between sine and cosine
input. R/D-converter's output is not linear. If I rotate the resolver one full
round, the output of the converter has 0-2 degrees of non-linearity. The
resolver is checked, and it is OK (only 5 arcmin error). What could be the
problem?

A

A phase difference of 2-3 degrees between the sine and cosine inputs is quite a
large phase difference and is the most likely cause of the errors. This phase
difference may be due to the resolver you are using or due to a mismatch in the
sine and cosine cables (different cable lengths or different loads could cause
this differential phase shift). For further information, refer to page 13 of
the datasheet, the section on differential phase shift. This section also
provides some suggestions for minimising the errors caused by differential
phase shift on the input signals.

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