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Modern Printed Circuits

Figure 3: Ground Track

“For designs that do not have large numbers of buses and are primarily embedded micros, hand routing is just as quick as auto-routing.”

Assuming I have a PCB outline I will create a physical representation and start placing connectors—the ones that just have to go somewhere. I glue on the connectors so I can’t accidentally move them. It is then important to check PCB size and the location of the connectors to see if they fit in the enclosure. I then start routing the board in one of two ways. Most of my boards are two or four layers. Regardless of the number of layers, I think about the board as a 3D object. The circuit layout can be broken down into two types: One type of layout deals more analogue circuits with short routes between a resistor and an IC or between a few caps and regulators (See Figure 1). The other type of layout is for digital circuit with long runs of two or more routes running between multiple devices. One example would be routing an SPI bus (See Figure 2). I try and start with the analogue circuits and lay out the components and tracks as they appear in the circuit diagram. If you

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Modern Printed Circuits: Sierra Circuits