The reference voltage for the ADS7887 and ADS7888 A/D converters are derived from the supply voltage internally. The supply to these converters must be driven with a low impedance source and must be decoupled to the ground Decouple the V_DD with 1-µF ceramic decoupling capacitors, as shown in Figure 40. Always set the V_DD supply to be greater than or equal to the maximum input signal to avoid saturation of codes.

Figure 40. Supply and Reference Decoupling Capacitors

Figure 41. Using the REF3030 Reference

Figure 42. Buffering With the OPA735