Decoupling capacitors are often recommended at 100nF, but this common practice is outdated and somewhat ineffective. To understand why, we need to consider the problem that decoupling solves and how it solves it in digital electronics. The dynamic load current, measured as dI/dt, is critical, and utilizing capacitors as low impedance paths for high frequency currents is key. While larger capacitors are better for decoupling in theory, real components have parasitics to contend with, such as equivalent series resistance (ESR) and equivalent series inductance (ESL), which can affect performance. Parasitic inductance, in particular, can impact the effectiveness of decoupling, underscoring the importance of placing decoupling capacitors close to the load to minimize the parasitic inductance in the path. Balancing parasitics and impedance at different frequencies is crucial for successful decoupling, making component selection and placement vital considerations for optimal performance.
https://codeinsecurity.wordpress.com/2025/01/25/proper-decoupling-practices-and-why-you-should-leave-100nf-behind/