In high-density and high-frequency applications are usually used four-layer board, the electromagnetic compatibility (EMC) in terms of better than the two board 20DB. In the case of a four-layer board, it is often possible to use a complete ground plane and a complete power plane, where only a few groups of circuit ground wires are required to connect to the ground plane and to handle the noise in particular.
There are many ways to connect from the ground of each circuit to the ground plane, including:
PCB design _ multi-layer PCB board grounding
PCB design _ multi-layer PCB board grounding
Figure: PCB design _ multi-layer PCB board grounding (a)
PCB design _ multi-layer PCB board grounding
PCB design _ multi-layer PCB board grounding
Figure: PCB design _ multi-layer PCB board grounding (2)
Between low frequency, low power and the same power supply layer, single point grounding is the most appropriate, usually used in analog circuits; generally use star connection to reduce the possible presence of the series impedance. High-frequency digital circuits need to be connected in parallel, and generally through the hole can be more simple way to deal with; generally all modules will be integrated using two grounding methods, the use of mixed ground way to complete the circuit ground and ground plane connection.
If you do not choose to use the entire plane as a common ground, such as the module itself has two ground when the need to split the ground plane, which often interact with the power plane.
Grounding need to pay attention to the following principles:
(1) Align each plane to avoid the overlap between unrelated power plane and ground plane, otherwise it will cause all ground plane segmentation to fail and interfere with each other;
(2) in the case of high frequency, the interlayer through the circuit board parasitic capacitance will produce coupling;
(3) The signal lines between the ground planes (such as the digital ground plane and the analog ground plane) are connected using a bridge, and the nearest return path is configured by the nearest through-hole.
(4) to avoid in the isolated ground plane near the clock line and other high-frequency alignment, causing unnecessary radiation.
(5) the signal line and its loop constitute the ring area as small as possible, also known as the minimum loop rules; ring area smaller, less external radiation, the external interference is also smaller. In the case of ground plane segmentation and signal alignment, the distribution of ground plane and important signal traces should be taken into account to prevent problems such as slotting of the ground plane.
Above is the PCB design in the multi-layer PCB board grounding, from two large aspects of a simple introduction to the multi-layer PCB board grounding and pay attention to the principle of how to.