What Is a Docupling Capacitor and How Is It Placed With EasyEDA x JLCPCB

What You will Learn From This Article

Filter circuits are used in many designs. Especially in circuits where the signal lines are carried by a long cable, fluctuations caused by the magnetic field outside should be filtered. These fluctuations can cause false signal detection and even break the processor with very high fluctuations.

Long-Wire Signal Line Filtering

Generally, filters containing capacitors are used to prevent such situations. Because capacitors can absorb sudden surges on themselves.

Capacitors used in filter circuits are simply called filter capacitors. But there is also a type of capacitor called a decoupling capacitor. Here we will see with examples what this capacitor does and how to place it with EasyEDA, JLCPCB's PCB design tool.

1. What is Decoupling Capacitor?

In fact, the decoupling capacitor is also the same as standard capacitors. Due to its area of use, it has only received a special name. Because the only purpose of the decoupling capacitor is not to prevent fluctuations in the line, but also to protect an integrated. For this, the placement of the capacitor should be as close to the integrated as possible. It is selected at a value of approximately 10nF. The capacity value may vary depending on the situation.

You can choose decoupling capacitors as a regular capacitor from JLCPCB's Assembly Parts Library.

A 10nF Capacitor From The JLCPCB Assembly Parts Library

You copy the JLCPCB Part Number of a capacitor you choose from here and open the Library section of JLCPCB's PCB design tool EasyEDA. You paste the copied JLCPCB part number here and add the resulting capacitor to your circuit.

Copying Part Number from JLCPCB Assembly Parts Library

Adding a Selected Component from the JLCPCB Assembly Parts Library to EasyEDA

The important thing here is the placement of this capacitor in the circuit. You should place this capacitor right next to the integrated we want to protect. Thus, even if the path is exposed to the magnetic field, a smooth current will enter the IC, with all fluctuations filtered before entering the full IC.

Remember, it's not enough to just filter a line from a remote point. While that line is traveling in the circuit, fluctuations may occur again by being affected by the magnetic fields formed in different ways. If you are not using a decoupling capacitor, these fluctuations will directly enter your IC.

Correct and Incorrect Positioning of a Decoupling Capacitor in EasyEDA, JLCPCB's Circuit Design Tool

2. Is Decoupling Capacitor Necessary?

Decoupling capacitor is not required. But its use is very beneficial in terms of integrated health.

The use of decoupling capacitors in the supply inputs of processors is a big plus in terms of circuits, especially in circuits with sensitive integrated circuits, circuits with sensitive measurement.

In addition, a decoupling capacitor in a 402 sheath with a value of about 10nF will not take up much space and can be easily added to many circuits. In EasyEDA, JLCPCB's PCB design tool, you can easily add this capacitor and simply protect your ICs.

3. Which Capacitor Type Would Be Best For Decoupling?

The best choice for decoupling capacitor will usually be small ceramic capacitors. Increasing the size and capacity of capacitors does not necessarily mean better filtering. Forget it. If you increase the capacitor's capacitance, you filter out lower frequency fluctuations. But the decoupling capacitor is especially used to filter out extremely high frequencies. I'm talking about frequencies above about 50 MHz.

Wrong Decoupling Capacitor Selection in JLCPCB Assembly Parts Library

Right Decoupling Capacitor Selection in JLCPCB Assembly Parts Library


Also, ceramic capacitors have a high temperature range. They have a wide voltage range and do a great job.

When choosing your decoupling capacitor, you can choose by considering them.

4. How Many Capacitors Should Be Used?

In most cases, the use of a single 10nF ceramic capacitor is sufficient. But your circuit may have too many high frequencies. There may be a lot of magnetic field in your circuit. You may be carrying high current in your circuit. A motor may be connected to your circuit and causing interference. In these cases, you may prefer to connect more than one decoupling capacitor in parallel.

Example of Multiple Decoupling Capacitors in EasyEDA, JLCPCB's Circuit Design Tool

Do not increase the value of the capacitor. This does not give you any more protection. Changes the frequency to be protected. You can use multiple 10nFs in parallel instead of increasing the capacitor value. If you have low-frequency interference in your circuit, you can also choose to parallel connect a smaller capacitor and a higher-capacity capacitor in parallel.

You can also follow Project 777 - Berkay EVREN - YouTube channel, which is the main sponsor of JLCPCB, for such tips and detailed design videos with EasyEDA.

JLCPCB Part-Time Engineer / Berkay EVREN