The EVM provides users the option to apply signals from any arbitrary signal source directly. Eight analog signals can be applied at terminal blocks J1, J3, J4, J5, J6, J7, J10 and J12. The ADS131E08 analog inputs are fully differential. Drive the analog inputs with one of the following general methods: pseudo-differential or fully-differential. Refer to the Analog Input section of the ADS131E08 data sheet for details regarding how to drive the ADS131E08 inputs. Refer to the Input Common-Mode Range section of the ADS131E08 data sheet for details on the usable input common-mode range of the analog front-end.

Each analog input channel includes an anti-aliasing filter that consists of series resistors, a differential capacitor, and common-mode capacitors. The anti-alias filter cutoff frequencies set by these components are:

Common mode filter cutoff :

Differential filter cutoff:

The differential capacitor value is 10 times larger than the common-mode capacitor. Choosing this ratio of capacitors sets the differential mode cutoff frequency approximately 20 times lower than the common-mode cutoff frequency. Using this ratio of filter cutoff frequencies prevents common-mode noise from being converted into differential noise due to component tolerances.

Figure 2-1 Analog Inputs