Components should be placed tightly

The analog signal must be short and direct, and the best way to achieve this is to start with a close location where the analog parts are well placed. This will not only simplify the direct routing of the traces, but will also help keep the analog and digital circuits separate. Also, remember to place the noisy analog part toward the center of the board instead of along the periphery. This will enable the ground plane and other circuits on the circuit board to help suppress some noise.

Provide isolation between analog and digital circuits

Since both analog and digital components can have a noise effect on each other, the best practice is to separate them as much as possible when placing the circuit board. With this separation of parts, you need to avoid routing high-speed digital traces through the analog circuit area. The noise of the digital signal will affect the analog circuit.

The signal must be short

At higher frequencies, impedance mismatches can cause analog signal reflections. These reflections can cause electromagnetic interference (EMI) in other components on the board. The best way to prevent this is to route the analog signal as short and directly as possible. Another good trick is to keep the traces on one layer, which will help reduce the number of vias and reduce the inductance of the circuit.

Circuit board design

Use dedicated analog ground

The digital ground plane on the circuit board will be busy with all digital signal return paths and will filter the power spikes generated by fast switching high-speed digital components. All these activities will cause a lot of interference to your analog circuit, so the best practice is to create a separate ground plane. The digital and analog ground planes can be connected at a single point, but it is important to keep them isolated.

Ensure a clear return path for analog signals

You must not only ensure that the traces of the analog signals are short and direct, but also the signal return path on the analog ground plane must be as smooth as possible. Designers often use vias, plane splits or cuts and gaps to prevent the direct return path of the signal from flowing. This blocking forces the return signal to linger around the ground plane, trying to find the shortest path back to its source, thereby generating unnecessary noise along the way.

These are the five points to keep in mind when laying out analog circuits. Remember, even with these suggestions, you still need to follow the Design for Manufacturing (DFM) rules to ensure that the board can be assembled correctly.