why my ad7794 can not achieve the correspoding effective resolution? the following is my configuration:
2 input signal: 20mV.dc and external bias voltage put in AIN1-.(disabled internal bias voltage)
3 chop enabled and fadc=16.7Hz
4 external reference 1,25V
5 contiuious sampling and no channel switch.
I have tried many mays to configure the ad7794 such as discrease the fadc, choose internal referrence or change the PGA. but the effective resolution don't fullfill my requirement. in the most configuration , the actual effective resolution is just 15.5. it is not match with the datasheet.
is it normal and do you have any suggestion ?
the schematic is very easy in the input channel. only LRC filter was added in the input channel.