The reference voltage for the ADS7886 A/D converter is derived from the supply voltage internally. The supply to ADS7886 should be driven with a low impedance source and should be decoupled to the ground. Decouple the VDD with 1-µF ceramic decoupling capacitors, as shown in Figure 32. Always set the VDD supply to be greater than or equal to the maximum input signal to avoid saturation of codes.

Figure 32. Supply/Reference Decoupling Capacitors

Figure 33. Using the REF3030 Reference

Figure 34. Buffering With the OPA735