Sunday, August 31, 2008

Component Placement

Components on a PCB operate a variety of edge rates and have varying levels of tolerance to noise. The most straightforward method for improving SI is to physically isolate components on the PCB according to their edge rates and sensitivity. An example is shown below. In this example, the power supply, digital I/O and high-speed logic are considered to be high-threat circuits to the sensitive clock and data converter circuits.

The first layout in above picture places the clocks and data converters adjacent to noisy components. Noise will be coupled into the sensitive circuits and their performance will be compromised. The second layout is much better as the sensitive circuits are physically isolated from the power supply, high-speed logic and digital I/O.

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