In my application, ADS1246 needs to sample a single ended signal from 0.2 to 4.8V, besides a differential signal.
But discription about input signal range and common voltage input range is not very clear in the datasheet of ADS1246.
With the datasheet, common voltage input range Vcmi is restricted from (AVss+0.1+VinPGA/2) to (AVDD-0.1-VinPGA/2), where Vin, as I understand, equals to AinP-AinN.
In the case that, AVDD=5V, AVss=0 (single supply), AinN=2.5V, PGA=1, Vref=2.5V:
When AinP=4.8V, Vin=AinP-AinN=2.3V, Vcmi should be in the range of 1.25V to 3.75V, and since VinN=2.5V, Vcmi is the common component of AinP and AinN, Vcmi=2.5V.
When AinP=0.2V, Vin=AinP-AinN=-2.3V, Vcmi range is from -1.05V to 6.05V, Vcmi, as the common component of AinP and AinN, is 0.2V.
As the result, when AinP is from 0.2V to 4.8V, Vcmi always satisfies the restriction in datasheet, which means I can use ADS1246 to operate AinP voltage from 0.2 to 4.8V when AinN=2.5V.
But, I cannot confirm this, since Vcmi range of -1.05V to 6.05V seems to be some wrong.
I want to realize about the Vcmi range of "(AVss+0.1+VinPGA/2) to (AVDD-0.1-VinPGA/2)" :
1. Does Vin equals to AinP-AinN, even when AinP<AinN.
2. Does Vcmi equals to the lower one of AinP and AinN, with the reference of GND.
3. Shall I use (AVDD-AVSS)/2=2.5V as the reference to calculate Vcmi.
Thanks a lot.