How to ensure interference immunity of EPS differential signal lines?

Ensuring the anti-interference capability of differential signals (such as CAN, RS485, USB, and driver complementary signals) in EPS is crucial, and routing is key. The core principle is to maintain the symmetry and tight coupling of differential pairs. Specific measures include:

1. Equal length and spacing: The two differential lines should always be parallel, with strictly matched line lengths (the error is usually controlled within 5-10 mil), and the line spacing should remain constant. This ensures that external common-mode interference is evenly coupled to both lines and canceled out at the receiving end.

2. Tight coupling: The two lines should be routed as close as possible (usually twice the line width), which enhances their immunity to common-mode noise and reduces external radiation.

3. Complete reference plane: The differential pairs should be routed above a layer with a complete ground or power plane, providing them with a defined return path and shielding.

4. Avoid crossing splits: Differential pairs must not cross ground plane splits, otherwise it will disrupt the return path and introduce common-mode noise.

5. Termination matching: Use appropriate termination resistors (such as 120Ω for CAN) at the receiving end to suppress signal reflection.