Question
I'm interested in additional register information to the configuration register
of the AD7194. It has 3 Gain bits to select the ADC input range. Is it possible
to also use Gain 2 or 4 (I assume a value of 1 or 2 to write to the gain bits).
In the current datasheet these bit setting is marked as reserved.
Answer
You are correct – if the gain bits are set to 1, a gain of 2 is selected while
a gain of 4 is selected if the gain bits are set to 2. However, when we
evaluated the part prior to release, we found that the INL breaks the datasheet
spec at a gain of 2 and 4. Therefore, we removed these gains i.e. they are not
documented in the datasheet. You can use these gains. However, specs are not
guaranteed for the part at these gains. For this reason and also because you
are designing a precise system, it may be better to use one of the documented
gains.