AD7795 calibration

Q 

We are using AD7795 in a product. Factory sys cal takes place at 60mV on
appropriate range. We now have a requirement to also add a lower range. Is
there a way of calculating the cal register values for the lower range from the
existing sys cal at 60mV ? Either directly or maybe by doing a self cal on the
lower range. I am trying to avoid having to cal at two points in production.

 

A 

If the PGA gain is changed, then a self calibration at least is needed to
remove the internal FS error of the PGA. If you are staying on the same gain,
then you could re-scale the offset and FS registers after initially performing
an internal calibration. See the last page on the attached FAQ which talks
about the 'weight' of an LSB in the offset and FS registers.
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