Figure 10 ESP8266EX PCB Layout
• On design of the crystal oscillator
Crystal oscillator should be placed adjacent to the XTAL Pins, the connection lines shouldn’t be too
long, and should be wrapped up for shelter.
The input and output lines cannot be punched, cannot cross the layers or be crossed.
The input and output bypass capacitor should be located near the chip; never set it on the lines.
No high frequency digital signal lines shall be placed under the four layers of the crystal oscillators.
The best choice is that no signal lines is placed under the crystal oscillator. The TOP layer where is
crystal oscillator is placed should be as large as possible.
Magnetic components, such as high current inductors, should not be placed near to crystal oscillator,
a sensitive component.
Figure 11 ESP8266EX Crystal Oscillators PCB Layout
• On design of the RF part
The characteristic impedance that RF lines should control is 50Ω, in order to ensure the complete
board in the second layer. The surrounding drilled hole should be blocked and the lines should be
as short as possible. !
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