Note that U4, a 10 MHz MEMS oscillator, is also very close to the microcontroller’s clock input pin. It’s always a good idea to minimize the length of traces carrying high-frequency digital signals. First of all, there are noise benefits: a shorter, more direct trace reduces the amount of noise that would otherwise be coupled into adjacent traces, and a shorter trace also reduces electromagnetic interference (EMI) because it is less effective as an antenna. The second issue is related to transmission-line effects. Minimizing trace length is a simple way to avoid problems related to signal reflections. However, reflection is not a significant concern at frequencies in the 10 MHz range, unless you are dealing with long interconnections or a very large PCB.
The decoupling capacitors (C4, C5, C6, C7, C9, C10, C11) are arranged around the perimeter of the chip, very close to their respective power pins and to the vias that connect the caps to the internal planes. Notice how the smaller cap is always closer to the power pin; this is because we rely more on the lower-value capacitor for high-frequency bypassing, and thus the first priority is minimizing the inductance and resistance between the smaller cap and the pin.
Nolanwebdev - Wiring Diagram Images Collection
Copyright © 2003 - 2018 Domain Media. All sponsored products, company names, brand names, trademarks and logos arethe property of their respective owners.