Hi,
You should keep analog and digital parts of your design separately. Use analog gnd and analog pwr for analog circuits and same for digital. Connect analog ground with digital gnd in only one point, same for power supply. Do not make loops. You should use 4 layer pcb, with two planes. Route digital traces over digital planes only, same for analog. Do not overlap analog plane over digital and vice-versa. If not possible (2 layer pcb), keep as far as possible voice traces from digital circuits, especially buses and clocks. Surround voice traces with copper connected to analog gnd.
Best,
/pisoiu