on the datasheet, it says it has a lower input range of +/- 7mV. I am kind of confused on how you got that lower input range and what it is actually referring too. Is it the actual range from AINP and AINN?
Hi Andrew,
Unfortunately this statement is not very clear.
The +/- 7mV comes from the minimum VREF (0.9V) divided by the maximum gain (128 V/V). Therefore, the maximum input range can be as small 7 mV. Rest assured, you can apply a 0V input!
Just for reference here are the ADC's input ranges for varying gains:
Hi Andrew,
The minimum allowable reference voltage for the ADS1261 is 0.9V. A 9mV reference would be way out of spec and result in very poor performance.
Instead of trying to scale the input signal to the ADC's full-scale range, it is much more important to make the measurement ratiometric to reduce the excitation voltage noise (see TIPD188). You can use the 5V excitation voltage as ADC's reference voltage, then errors in the reference voltage (such as noise) will tend cancel, since they will be common to both the input and reference voltages...
Very few external amplifiers have better noise performance than the ADS1261's internal PGA, so connecting the load cell directly to the ADC (as shown above) is going to give you the best resolution.
