This is a basic planning strategy that costs virtually
nothing and yet has the potential for saving considerable time and money should EMC
problems are encountered down the road. A great deal of EMC problems are related to I/O
cables, which often play a vital part in product emissions exceeding limits and cables
acting as antennas when picking up spurious interference from external sources. The
provision of adequate space on the circuit board for the future addition of components
such as capacitors, diodes, MOVs, ferrites and other EMI suppression components can be
implemented using a combination of tracks, lands and jumpers to anticipate the possible
addition of these components in the future. Designers may be tempted to skip this approach
in order to save a few computer keystrokes and jumpers but those who do would often find
themselves or their frustrated colleagues hacking up the board with a knife to make room
for EMI suppression components after the first trip to the EMC test lab. The costly
turn-arounds associated with PCB rework can often be avoided if this EMC consideration is
factored into the PCB design process.
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EMC Tip 12 |