10 General board layout guidelines
10.1 Traces recommendations
A right angle in a trace can cause more radiation. The capacitance increases in the region of the corner and the characteristic
impedance changes. This impedance change causes reflections. Avoid right-angle bends in a trace and try to route them with at
least two 45° corners. To minimize any impedance change, the best routing would be a round bend, as shown in
Figure 27.
on
page 27.
Figure 27. Poor and correct way of bending traces in right angles
To minimize crosstalk, not only between two signals on one layer but also between adjacent layers, route them 90° to each other.
Complex boards need to use vias while routing; you have to be careful when using them. These add additional capacitance and
inductance, and reflections occur due to the change in the characteristic impedance. Vias also increase the trace length. While
using differential signals, use vias in both traces or compensate the delay in the other trace.
10.2 Grounding
Grounding techniques apply to both multi-layer and single-layer PCBs. The objective of grounding techniques is to minimize the
ground impedance and thus to reduce the potential of the ground loop from circuit back to the supply.
• Route high-speed signals above a solid and unbroken ground plane.
• Do not split the ground plane into separate planes for analog, digital, and power pins. A single and continuous ground
plane is recommended.
• There should be no floating metal/shape of any kind near any area close to the microcontroller pins. Fill copper in the
unused area of signal planes and connect these coppers to the ground plane through vias.
NXP Semiconductors
General board layout guidelines
Hardware Design Guidelines for S32K1xx Microcontrollers , Rev. 3, December 2018
Application Note
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