Project Summary

Objective -

• Demonstrate importance of placing decoupling capacitors close to Vcc lead of ICs for switching signal integrity.

• Demonstrate importance of separate ground vias for each return path for switching signal integrity.

• Demonstrate importance of making return paths to ground vias as short as possible.

Strategy -

• Create example of good and bad layout for signal integrity

• For good layout, Place separate ground vias as close to last electrical component in return path. Opposite for bad layout

• For good layout, Place decoupling capacitors closest to Vcc leads of ICs. Opposite for bad layout.

• For bad layout, use as few cross-unders as possible to keep return plane continuous. Opposite for bad layout.

Conclusion -

• In bad layout section, when all return paths were routed to single ground via, hex-inverter signal was very poor.

• In good layout section, when all return paths were routed to seperate ground vias, hex-inverter signal was sharp.

• Long wire from decoupling capacitor to Vcc lead caused sharp dip in power supply voltage when IC was drawing current.

• Non-continuous return plane induces emf that affects signal integrity.