Requirements for Electrical Characteristics In Wiring

Requirements for Electrical Characteristics In PCB Wiring:

1. Impedance control and impedance continuity

Avoid sharp and right-angle traces.

Use as few vias as possible for critical signal routing.

Appropriate consideration of arc wiring for high-speed signal lines.

2. Control requirements for crosstalk or other interference such as EMC

High-speed signals and low-speed signals need to be layered and partitioned.

Digital signal and analog signal layered partition wiring.

Sensitive signal and interference signal layered and partitioned wiring.

The clock signal should go to the inner layer first.

Do not lay copper wires under the projection area of ​​inductive devices such as power inductors and transformers. Because there will be parasitic capacitance between the coils and parallel resonance with their inductance, there will be SRF, and SRF is related to EPC, so the smaller the EPC, the better, to ensure a wider frequency range of inductance. SRF needs to be at least DC -10 times the switching frequency of the DC Converter, for example, if the switching frequency is 1.2MHz, the SRF needs to be at least 12MHZ. Therefore, when layout, the power inductor should be hollowed out, and there should be no metal to avoid generating additional EPC, resulting in an inductive frequency scope reduction.

The key signal should be placed on the preferred layer, with the ground as the reference plane.

Consider using packet ground processing for critical signals.

It is one of the important principles of EMC design to avoid loops in any signal, including the return path of the signal.