11.1.2 Si5341 Crystal Layout Guidelines
The following are five recommended crystal layout guidelines:
1. Place the crystal as close as possible to the XA/XB pins.
2. Do not connect the crystal's GND pins to PCB gnd.
3. Connect the crystal's GND pins to the DUT's X1 and X2 pins via a local crystal shield placed around and under the crystal. Make
sure that X1, X2, and both crystal ground pins do NOT connect to the pcb ground. See
Figure 11.1 64-pin Si5341 Crystal Layout
Recommendations Top Layer (Layer 1) on page 47
for an illustration of how to create a crystal shield by placing vias connecting
the top layer traces to the shield layer underneath. Note that a zoom view of the crystal shield layer on the next layer down is
shown in
Figure 11.2 Zoom View Crystal Shield Layer, Below the Top Layer (Layer 2) on page 48
.
4. Keep transitioning signal traces as distant as practical from the crystal/oscillator area especially if they are clocks or frequently
toggling digital signals.
5. In general, do not route GND, power planes/traces, or locate components on the other side below the crystal shield. If necessary, a
ground layer may be placed under the crystal shield plane as long as it is at least 0.05” below the crystal shield layer.
Figure 11.1. 64-pin Si5341 Crystal Layout Recommendations Top Layer (Layer 1)
Note the vias that are shown for the center ground pad so that there is a low-impedance path to ground and a good thermal path to
ground. See
for details on these vias.
The following figure shows the layer that implements the shield underneath the crystal. The shield extends underneath the entire crystal
and the X1 and X2 pins. This layer also has the clock input pins. The clock input pins go to Layer 2 using vias to avoid crosstalk. As
soon as the clock inputs are on Layer 2, they have a ground shield above below and on the sides for protection.
Si5341, Si5340 Rev D Family Reference Manual • Crystal and Device Circuit Layout Recommendations
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.3 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 26, 2021
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