Should I separate digital and analog ground planes on my evaluation board?

Separating analog and digital ground planes is a good idea, but not always necessary. It is often very difficult to implement properly, so one should proceed with caution. All of our evaluation boards use a common analog and digital ground plane, but with separate power supply planes.

Separating digital and analog ground planes will help keep digital switching transient ground currents from contaminating the analog circuitry. In many of our earlier products (AD9850, AD9851, AD9852, AD9853, AD9854, AD9856, AD9857) the benefit gained from separating ground planes was minimal at best. However, in later products, the AD9858, AD9951/52/53/54 and AD9859, separating the ground planes can help to isolate the SYNC-CLK from the analog output.