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Temporary/PCB Design Review.md

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+---
+title: PCB Design Review
+created_date: 2025-02-12
+updated_date: 2025-02-12
+aliases:
+tags:
+---
+# PCB Design Review
+
+## Rise Time vs Length
+The rule of thumb is that a track length shall be shorter than 1/6th of the rise time. According to [this comment](https://electronics.stackexchange.com/a/258992) the rule of thumb can be applied like this (example with 100MHz signal):
+First lets calculate the wave length in free space:
+$$\lambda = \frac{c}{f} = \frac{3*10^{8}}{100*10^6} = 3m$$
+In a PCB you can take roughly $\frac{\lambda}{2}$ as the wavelength, which would be $1.5m$. 
+One sixth of this results in roughly $25cm$.