Simply put, the digital ground is the common reference terminal of the digital circuit part, that is, the reference terminal of the digital voltage signal; The analog ground is the common reference terminal of the analog circuit part, and the voltage reference terminal (zero potential point) of the analog signal.
The reason for dividing into digital and analog ground:
Due to the fact that digital signals are generally rectangular waves with a large number of harmonics. If the digital ground and analog ground in the circuit board are not separated from the access point, harmonics in the digital signal can easily interfere with the waveform of the analog signal. When analog signals are high-frequency or strong electrical signals, they can also affect the normal operation of digital circuits. Analog circuits involve weak signals, but digital circuits have higher threshold levels and lower power requirements than analog circuits. In systems with both digital and analog circuits, the noise generated by the digital circuit can affect the analog circuit, causing the small signal indicators of the analog circuit to deteriorate. The solution to overcome this is to separate the analog ground and digital ground.
The fundamental reason for the problem is that the resistance of the copper foil on the circuit board cannot be guaranteed to be zero. At the connection point, the digital ground and analog ground are separated in order to minimize the common ground resistance between them.
