I want to design a four-layer board with a PIC32MM0256GPM048T microcontroller. All components must be on the top of the board. I tried routing OSC1 (osc in) and OSC2 (osc out) lines, and placing the load capacitors (0402 C0G) near to the crystal (18.432 MHz, 2520 package), but I am not sure that is correct.

The decoupling capacitors (and GND line) are also near to the crystal's tracks.

Will it cause any problem?

Thanks for the help.

Layout of tracks on PCB

Artificial 3D image of populated PCB

  • \$\begingroup\$ Is that the recommended ground layout for the oscillator? You may have issues with reflow soldering having such large heatsink copper areas. \$\endgroup\$ – Ron Beyer Mar 10 at 20:53
  • \$\begingroup\$ @RonBeyer I don't think so, the 2 ground pads are on complete opposite side so surface tension should be even. \$\endgroup\$ – eeintech Mar 10 at 21:56
  • \$\begingroup\$ Are you trying to create a ground island around the crystal? What's on your L2/L3 and bottom layers? \$\endgroup\$ – eeintech Mar 10 at 21:57
  • \$\begingroup\$ Microchip recommended guard ring around the crystal, but I think this is not necessary for four layer board. My stack up is that: Signal - Ground plane - Power plane - Signal. I avoid to route any signal under crystal lines. I don't want to create ground island around the crystal because I think it add more parasitic capacitance to XTAL pins, I want to minimize this. I tried to route crystal lines as diff pair to avoid some phase shift. I added some ground VIAs near to the load capacitors to minimize ground return current path impedance. I don't know that my design how is right. \$\endgroup\$ – slimcolt Mar 11 at 7:50

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