AD7792: FAQs

Q 

Do I need to perform calibrations for each channel
and do I need to do this each time I change channel?

A 

With the AD7792, there is no need to calibrate the offset as the ADC takes care
of this. A full-scale calibration is required for each channel. So, as part of
the initialization routine, each channel to be used should be selected, the
gain, output data rate for the channel set and an internal FS calibration
performed. Each channel has its own offset and gain registers. Therefore, each
channel only needs to be calibrated as part of the initialization routine. When
a channel is selected, the offset and gain registers for that channel are
automatically selected. Further calibrations are only needed if the customer
wishes to re-calibrate because the temperature has changed significantly.
However, for many applications, additional calibrations are not required. It
really depends on the error budget for the application. However, the
calibration on power up is required.

So, the initialization routine is

Select channel 1
Calibrate channel 1
Select channel 2
Calibrate channel 2
Select channel 3
Calibrate channel 3

The conversion routine will be

Select channel 1
Wait until DRDY goes low (120 ms when the 16.7 Hz output data rate is used)
Read conversion
Select channel 2
Wait until DRDY goes low
Read conversion
Etc.