This is my current PCB crystal set up. The crystal run at 16 Mhz. Any thoughts/comment?

enter image description here


MCU - Datasheet

TI PCB guideline Tiva C - Here

  • \$\begingroup\$ Can you add a link to the MCU's datasheet? \$\endgroup\$ – Bence Kaulics Jul 7 '15 at 18:50
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    \$\begingroup\$ At 16MHz u shouldn't have issues. But u can make things better. You should relocate crystal closer to MCU. Also, it seems you connect your capacitors on your ground plane by a via. Try to make a local ground and so, connect it to your ground plane. But, as I said, for 16MHz I think it's okay \$\endgroup\$ – Pedro Quadros Jul 7 '15 at 18:55
  • \$\begingroup\$ The POV on previous capture was bad, we couldn't see the high speed USB differential pair. \$\endgroup\$ – MathieuL Jul 7 '15 at 19:00

My comment would be, What is your total trace Length, it is looking maybe a bit long? From the PCB Guideline:

3.7.2 Crystal Oscillator Circuit Layout

The key layout objectives should be to minimize both the loop area of the oscillator signals and the overall trace length. A poor oscillator layout can result in unreliable or inaccurate oscillator operation and can also be a noise source. Ideal trace length is less than 0.25 in or 6 mm. Do not exceed 0.75 in or 18 mm.

  • \$\begingroup\$ That what I thought, but is I bring the crystal closer the MCU, isn't there a chance that the crystal will affect the USB lines. Ortherwise, I could move the USB connector. \$\endgroup\$ – MathieuL Jul 7 '15 at 19:07
  • \$\begingroup\$ Move the osc to the left without moving it up. Move those other two components if needed. \$\endgroup\$ – scld Jul 7 '15 at 19:14
  • \$\begingroup\$ Finaly, I choose to move the USB connector, the crystal is a vital part of the design, therefore I don't want to be near the worst value. \$\endgroup\$ – MathieuL Jul 7 '15 at 19:19
  • \$\begingroup\$ I also recommend widening the traces as much as possible. This decreases the resistance and will give you a nicer oscillation \$\endgroup\$ – DerStrom8 Jul 8 '15 at 15:14
  • \$\begingroup\$ Unrelated, but your USB Traces do not appear to have the correct width / spacing to achieve the correct impedance nor do you have a TVS (which may or may not be needed depending on your intended usage.) \$\endgroup\$ – user69821 Jul 10 '15 at 13:09

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