Signal Integrity, Si - Nuvoton ARM ARM926EL-S User Manual

Signal integrity, SI

Due to 2- layers PCB does not have a separate GND plane, and to ensure the connectivity and
integrity of the GND plane, the following requirements must be observed:

The Bottom layer as far as possible or less device, to ensure the bottom surface of the GND
integrity. Especially at the bottom of the main chip.,the NuMaker-emWin-RDK-N9H20 demo
board that GND process at the bottom of main chip is shown in the following figure.

If that is possible please place more via holes to GND to ensure that the top surface and the
bottom surface of the GND copper skin connectivity.

Ensure that there is no island of GND copper skin, as far as possible to ensure that as much as
possible to connect the copper, so that the signal return path as short as possible.

High-speed signal line under the bottom surface, as far as possible to ensure the complete GND
plane, do not have to walk through the line.

For critical signals, such as crystal oscillator, System Reset, I²C, USB, etc., need to be
processed with shield GND all the way. The good shield GND process can guarantee the
continuity of the impedance, anti-interference, and prevent EMI radiation.
The following fugure is the LCD_CLK signle connectivity with shield GND process
Mar. 26, 2021
NuMaker-emWin-RDK-N9H20
Page 11 of 25 Rev 1.11