I really appreciate your help.
There is another question:
Q: Under what condition or application would you recommend enabling the buffer inside ADS1224?
I do understand the enabled buffer will increase the input impedance of ADS1224 greatly, which would guarantee a more accurate sampling that is more close to the actual input signal connected to the input pins. However, compared to the condition without buffer, I also find that an enabled buffer will result in a slightly poor effect on the performance like input voltage range, INL, gain error, and gain error drift, which shown on page 3.
In brief, the buffer is like a double-edged sword and I don't know the suitable usage. This is why I ask this question.
Thanks for your time.