Digital circuit and analog circuit common ground processing
Many PCBs today are no longer single functional circuits (digital or analog), but are made up of a mixture of digital and analog circuits. Therefore, it is necessary to consider the interference between them when lining, especially the noise interference on the ground.
Digital circuit frequency is high, and analog circuitis with high sensitivity. For signal lines, high-frequency signal lines are as far as possible away from the sensitive analog devices, For ground line, PCB has only one node to the outside world, so must settle PCB common digital and analog grounds problem, However, the digital circuit and analog circuit inside the board are actually separated from each other, and they are not connected to each other, only at the interface between the PCB and the outside world (such as plug, etc.). There is a little short connection between the digital and analog ground, please note that there is only one connection point.There are also not common ground on PCBs, which are determined by the system design.