The Importance of Ground Pins: Lessons in Signal Integrity

I was laying down some connectors, and a reviewer goes, "Yo! Add more GNDs." I thought, "We already have GND pins!" But here's the thing: GND pins next to signals are CRUCIAL for signal integrity.

EVERY signal is differential. Yup, even "single-ended" signals; they return through 0V, which is easy to forget! So, placing them additional 0V close to signal wires reduces loop area and interference.

Imagine two boards powered via 1m wires. Without return wires, an AC signal travelling 10cm creates a 2m return path, forming a huge loop. This loop causes significant cross-talk, especially with fast rise times like a 1MHz SPI clock with 10ns edges.