03/07/2025 5:56 am
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I’m designing a circuit with a microcontroller and some digital ICs, and I want to ensure power stability and noise suppression using decoupling capacitors.
How do I select the right capacitor value based on the components used?
Are there standard values for typical microcontroller circuits, or does it depend on current draw, switching speed, or PCB layout?
Since I want to avoid glitches or resets due to power instability, I’d like to understand how to choose these capacitors correctly instead of just following rules of thumb.
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05/07/2025 5:28 am
Decoupling capacitors are essential for stabilizing the power supply and suppressing noise in microcontroller and digital circuits. A common starting point is placing a 100 nF ceramic capacitor (X7R type recommended) close to the Vcc and GND pins of each IC to handle high-frequency transients.
To support sudden current demands and filter lower-frequency noise, it's also good practice to add a bulk capacitor—typically 1 µF to 10 µF—near the microcontroller or groups of ICs. The exact values depend on several factors, including the switching speed of the ICs, current consumption, and the quality of the PCB layout.
Faster ICs may require additional smaller capacitors like 10 nF or 1 nF in parallel with the 100 nF to cover a broader frequency range. High-current circuits may benefit from larger bulk capacitors up to 47 µF. Proper placement is critical—capacitors should be located as close as possible to the power pins, with short, direct traces.
Using a mix of capacitor values in parallel helps improve overall decoupling performance. While 100 nF is a solid default, evaluating layout and load conditions can help you fine-tune your choices for a more robust and reliable design.
