I use the 4-20mA current output and cannot achieve the specified accuracy.
Example at 20°C: set value 20mA, measured value 19.9772mA which gives an error of -0.114% FSR.
Such a high deviation is not expected at a constant temperature since the TUE is +/-0.15% FSR over the full temperature range!
Several configurations (internal/external reference, Rset, boost etc.) were tested without success. Schematic and measurement results are attached.
Please consider and give a hint. Thank you very much!
Apologies for the delay. Just some quick points:
Thank you, Mark!
Indeed, our measurements comply to the datasheet, if interpreted correctly. They have been confirmed by measurements on the EVAL board as well.
Unfortunately, the definition of the TUE and FSR% is not clear. The above link is an eye opener. Why isn´t it explained in that way in the dataseet (there is a comment, but quite hidden)?
To be honest, it is quite difficult to estimate the real behavior of the device by reading the datasheet only. We have invested high effort in fundamental investigation and analysis to figure out the characteristics. Only after measuring we understood the datasheet..... should be vice versa......
Just to complete the discussion:
- We have used the B-type of the AD5422 in all measurements (the schematic say A-type which is misleading).
Thanks a lot for your advice!