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Routing Netlist on PCB.
General PCB routing guidelines.
As first rule of routing keep your routs short. Sticking to this rule will be easy if you follow above placement guidelines properly. Long routs will easily generate noise or will pick up noise. Long routs connected to sensitive device will pick up noise by route acting as antenna and if long trace carry decent amount of signal energy, it will act as transmitting antenna.
If you have long traces routed close to each other, there is good chance that you will end up with board which has cross-coupling or cross-talk between routes. This cross-talk could make your design completely non functional. Cross-talk is often found in RF designs, high performance analog designs and high speed digital designs. In simple most advanced designs could be affected by cross-talk. If you have high speed clock trace, make sure that line does not go closer to your input of high gain op-amp. If you going to make multilayer board, running long traces on top of each other could create cross-talk. Signals like parallel address busses are not affected by cross talk.
When you routing multi layer board, vias will be used. If you going to fabricate your PCB professionally, via count is not much important. However if you plan to fabricate PCB your self, try to keep via count low. Also remember that vias can also contribute to couple signal noise. So make sure you place your sensitive traces away from vias which generate noise.
Interference susceptibility increases with increasing impedance, frequency and gain. Therefore if your design has high gain op-amps or RF circuits make sure inputs to and outputs from these components are properly separated
Continue reading for general purpose analog PCB design routing and placement guidelines
