Grouping Components
Grouping Components
Different Susceptible Systems
Different Susceptible Systems
Low Speed Digital
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
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
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
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
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