Reducing Crosstalk and Distortion
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• Self shielding occurs when the return current is allowed to surround the outgoing current, as in a coaxial cable.
• Traces on adjacent layers should be oriented perpendicular to one another.
• Ringing may indicate excessive wiring inductance.
• Rounding may indicate excessive capacitance.
• Unintended sharp transitions in signal level may indicate reflections due to impedance mismatches.
• Separate high current, low frequency (kHz) return paths (ground) from low current return paths. Connect the high and low current returns together at only one point.
• Connect “guard traces” to the return plane on both ends so that the traces can serve as additional signal return paths.
• Do not allow any electrically floating metal.
• Connect all metal fill areas to the return plane.
• Connect all unused integrated circuit gate inputs to either return (ground) or +VDC .
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