Grouping Components

Different Susceptible Systems

Low Speed Digital

• Not very susceptible to noise
• Generates a medium amount of noise, so keep it away from the most noise sensitive circuits
• The most active signals are the most noisy
• Other than that, layout is not too critical and this can be placed around the board as kind of a “filler” in places where nothing else will want to go and can be easily auto-routed.

High Speed Digital

• Same as low speed digital, plus the following:
• There can be a very high number of interconnecting traces
• Generally uses controlled impedance traces
• Requires controlled, minimized, or matched signal delay times and proper location of termination devices
• Can generate some serious heat - added copper planes to conduct heat away and heat sinks will need to be designed in

Analog

• Usually very sensitive to noise pickup
• Keep away from noise generators
• High impedance nodes and nodes followed by a lot of gain are generally most sensitive to noise
• Look for recommended grounding and shielding in application notes
• May also be sensitive to surface leakage currents, temperature, etc
• Power amplifiers may generate significant heat - added copper planes to conduct heat away and heat sinks will need to be designed in

Power

• Can generate a lot of noise (esp. switching power supplies, class D amplifiers, etc)
• At the same time, some nets are very sensitive to noise (i.e. sense and feedback nets)
• Can generate a lot of heat - added copper planes to conduct heat away and heat sinks will need to be designed in
• Switching nodes are sensitive to layout parasitic inductance and capacitance
• Keep high AC currents confined to small loop areas to reduce noise
• May involve high voltage and safety issues, special spacing and insulation requirements

RF

• Uses controlled impedance traces
• May require traces to be designed as antennas (requires RF design background)
• Receivers are very sensitive to noise
• Transmitters generate noise and dissipate heat proportional to the power involved
• Again, added copper planes to conduct heat away and heat sinks will need to be designed in
• Requires special attention to shielding and grounding