What should be considered in the PCB design of crystal oscillator circuits?
A.
Layout Design Considerations are as follows:
- Proper Positioning: The internal component of the crystal is a quartz blank, which is fragile and can easily break if dropped or subjected to impact. Therefore, place the oscillator away from the edge of the board and close to the MCU.
- Close Coupling: The coupling capacitors should be placed close to the power pins of the crystal oscillator. If several coupling capacitors are used, arrange them in the direction of power flow, with capacitance values from large to small. The crystal itself should be positioned as close as possible to the MCU.
- Short Traces: Keep all traces connecting the input and output terminals of the crystal as short as possible to reduce noise interference and the impact of parasitic capacitance on the crystal.
- High Isolation: Ensure that there are no other components surrounding the crystal to prevent mutual interference, which can affect clock signals and the quality of other signals. Maintain a 1mm clearance around the crystal for other components and a 0.5mm clearance for via routing. Avoid placing vias (including ground vias) directly underneath the crystal.
- Ground the Enclosure: The enclosure of the crystal must be grounded to prevent radiation from the crystal and to shield it from external interference.