How to Place and Install Decoupling Capacitors During PCB Layout

Decoupling capacitors are components used to reduce high-frequency noise and electromagnetic interference in a circuit. They can also provide power to an IC. This article will discuss the placement guidelines for these capacitors. By following these guidelines, you will be able to design a circuit with lower costs and less risk of manufacturing errors.

Reduces high-frequency noise in power supply signals

Noise in power supplies can negatively affect the performance of a device. This unwanted energy is often generated by high-frequency power conversion switching circuits. Noise can also be radiated from wires or PCB traces. Several practices can help minimize noise in power supplies. Here are three common practices.

First, identify the source of the noise. This noise can originate from many different sources, including switching-frequency noise and ringing after switching transitions. The noise can also be caused by multiple switching regulators in a system. This type of noise can be reduced with signal analysis techniques.

In addition to shielding cables, use enclosures and filters to reduce radiated noise. Enclosures with openings that are a quarter wavelength or smaller can reduce most of the noise. If you are using a data acquisition unit, make sure that the enclosure is designed to minimize noise radiated from the equipment.

Reduces electromagnetic interference

Decoupling capacitors are used in circuit boards to prevent interference from stray electromagnetic waves. In PCB layout, capacitors are installed on the power plane and on the ground plane. This separation prevents parallel capacitances, which can cause problems in electromagnetic compatibility. In addition, capacitor PCBs have uniform distributions and high frequency response. To achieve the best results, these components should be placed close to power and ground planes. Circuits that produce high power and high speed signals should be placed close to the ground plane and circuits that produce low power and low frequency signals should be laid closer to the surface or power plane.

When installing decoupling capacitors on PCB layout, make sure you select capacitors with high value that are located as close to the source of interference as possible. They should also be placed near the connectors for input signals. Ideally, these capacitors should be placed in series with the trace. It is recommended to select capacitors that are at least 10 times larger than the total decoupling capacitance of the circuit.

Can provide power to an IC

Power-supply pins are the terminals used to provide voltage and current to an IC. Typically, an IC has two power-supply pins. These pins are connected to the power rails of the circuit. The pins are labeled differently depending on the manufacturer and family of ICs.

Placement guidelines for decoupling capacitors

When designing a PCB layout, decoupling capacitor placement is an important step to ensure the power and signal integrity of the board. By following the proper placement guidelines, you can ensure that the capacitors are placed in optimal locations. These guidelines can be found in the component datasheet.

In a PCB layout, decoupling capacitors are typically placed on the same layer as the digital ground pour. They are also sometimes connected between two separate PCB ground pours. Decoupling capacitors must be placed close to component pins to ensure smooth current flow in the plane. When designing a decoupling capacitor, it is recommended that it have the highest nominal capacitance possible.

In addition to following the placement guidelines above, decoupling capacitors should be placed as close as possible to the voltage pin of the component. This helps reduce overall connection inductance and improve high-frequency filtering.