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AD2S82A: Maximum tracking rate.

We need the maximum resolution of conversion in the entire range of the motor
(0-1350rpm). AD2S82 datasheet says that 16bit resolution is allowed only up to
975rpm. Discarding what datasheet says I calculate the value of R6 for 1750rpm
using 16bit resolution and we try to spin the motor. We were able to operate
without any problems for the entire range of the motor, so the question is: can
we trust to use this hardware setting or in long term there could be some
We have also another application where the motor is 20000rpm and we need to use
at least the 12bit resolution.


The AD2S82A operates as a tracking resolver-to-digital converter and forms a
type 2 closed loop system. The output will automatically follow the input for
speeds up to the selected maximum tracking rate. If the maximum tracking rate
is exceeded the signal at the output of the phase-sensitive detector (DEMOD
O/P)will increase and the converter will be unable to reach a null.

The factors which affect the maximum tracking rate are discussed in page 3 of
the application note AN-264 Dynamic Characteristics of tracking converters.