High Speed PCB PDN Problem

In high speed pcb design, well-designed PDN is very important to the final electrical performance of the circuit board. If there is no clear signal return path in high speed pcb design, high speed pcb products may generate a lot of noise, resulting in wrong signals, interference with the normal operation of the circuit, and other high speed pcb signal integrity problems. Such as EMI and ground bounce. In the process of high speed pcb design, the return signal that cannot find a clear return path on the reference plane may eventually be coupled to any return path that the high speed pcb can find, including other routes. This unintentional coupling will generate common-mode current. Common-mode currents may produce electromagnetic radiation and introduce additional noise problems.

Suggestions for high speed PCB design PDN

In order to avoid the problems mentioned above, the following are PDN recommendations for high speed pcb design:

1. 1. PDN of high speed pcb design shall be set with a continuous grounding plane rather than a split grounding plane. When wiring high speed pcb transmission lines, ensure that they have a clear signal return path across the adjacent ground plane.

2. 2. High speed pcb design PDN should be careful with circuit board features that may block the ground plane. If a high speed pcb design PDN has too many through-holes, board cuts, or other obstructions in a centralized area, it can disrupt a clear return path on the reference plane.

3. 3. High speed pcb design PDN has multiple power supply connections of large pin number high-density devices. Each connection needs to be as close as possible to the bypass capacitor of the power supply pin to obtain the best power filtering effect.
   
   

High speed pcb routing guidelines

When the components on the PCB board are properly laid out, there will be a basic high speed pcb template. The following are guidelines for high speed pcb wiring.

1. 1. High speed pcb wiring shall ensure that the design rules and constraints of line length, matching length, width, spacing, layers, impedance controlled wiring parameters, differential pair, routing adjustment, and via allocation are fully followed.

2. 2. In the design of high speed pcb, any necessary area rules shall be set according to the unique wiring requirements, and the prohibited wiring area shall be reserved.

3. 3. In addition to specific cabling topology and measurement length, the high speed pcb should be designed to keep the cabling short and direct.

4. 4. In the design of high speed pcb, do not wire in the gap or disconnection of the grounding plane.

5. 5. When wiring high speed pcb signals, ensure that they have a clear signal return path on the adjacent ground plane.

6. 6. For sensitive signals, the high speed pcb should be designed to ensure that there is an additional gap between them and other cabling, usually three times the width of the standard cabling.

7. 7. Ensure that the high speed pcb transmission lines are arranged on their assigned layers to ensure their return paths on adjacent reference planes.

8. 8. Avoid changing layer attributes through the high speed pcb transmission line.

9. 9. Be careful with parallel high speed pcb transmission lines.

10. 10. Pay attention to the crosstalk in the vertical direction between layers in the high speed pcb cabling. The distance between layers may be smaller than that between two parallel lines on the same layer.

11. 11. The high speed pcb uses wider routing in analog cabling.

12. 12. In the design of high speed pcb, a wider grid can be selected to place vias, and vias escape can be planned for the maximum number of routing channels.

13. 13. In the design of high speed pcb, the use of visas should be minimized to reduce inductance. Blind holes, buried holes or microphones can be used.

14. 14. In the design of high speed pcb, pay attention not to block the return path on the grounding plane in the area with dense dispersed vias.

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