Hi Shlomi,
Welcome to the TI E2E Forums!
The ADS1256 can measure a +/- 5V signal; however, it must be a differential signal with a common-mode voltage around 2.5V (and the internal buffer must also be disabled). Please refer to the analog input voltage specification...
Notice that the "absolute input voltage" is specified for -0.1 to 5.1V (buffer off) OR 0 to 3V (buffer on) , for AVDD = 5V.
Therefore, into order to measure a +/5V signal, the input signal needs to be differential. For single-ended inputs, you are limited to 1/2 of this input range. Assuming that the negative input is fixed to 2.5V, the positive input can swing from 0-5V, resulting in a +/-2.5V differential signal (buffer off), OR with the buffer off you can swing from 0-3V (for a maximum of +/- 1.5V, assuming that the negative input is fixed to 1.5V).
Does that make sense?
Refer to the common-mode calculator here to verify if your input signals can be measured by the ADS1256: http://www.ti.com/lit/zip/sbac145
Best regards,
Chris
