Electronic noise in printed circuit boards (PCBs) can adversely affect the operation of the circuit. This is especially true for circuits that operate at frequencies in MHz range and higher. This is because at high frequencies, electromagnetic waves that are created around the traces and inside components can be picked up by other traces and components. This may result in degradation of performance through changes induced in the shapes of current and voltage pulses. Reducing noise and its adverse effects requires careful PCB layout designing.
1 While designing the PCB layout, try to cover as much board area as possible with ground and power planes. It is a good practice to keep one face for ground plane and the other for power plane.
2 While designing the PCB layout, keep the signal traces as thin and as small as possible. Use board vias if required to keep the traces small. Traces that are less than 8 millimeters thick are generally considered good at reducing capacitive coupling, which picks up noise. The separation between adjacent traces should be greater than the width of the traces, otherwise significant cross talk can occur between them.
3 Keep the analog and digital circuitry separate on the PCB. Digital circuitry produces high-frequency digital noise that can induce errors on digital as well as analog sides if the circuits are not sufficiently separated.
4 Keep the traces, especially the sensitive ones, away from oscillators. Never run any trace underneath an oscillator.
5 Use high-value, high-quality tantalum-polarized capacitors to filter noise from regulators and power supplies. You can also use ferrite beads to filter incoming power. Also, for filtering power input to electronic chips, use high-quality tantalum-polarized capacitors as close to power pins as possible.
6 Avoid using 90-degree turns on traces. If a 90-degree turn is desired, use two 45-degree turns instead.