I've completed a few circuit board layouts before, however this is my first time doing a layout with a oscillator/MCU. After doing some reading (via this site and datasheets) I've come up with the following layout.
- 2 layer board
- 16MHz crystal (5x3 SMD package)
- TQFP44 MCU
*Note that local ground connections on the top layer (MCU) are drawn over the silkscreen. This was done in MSPaint to increase readability.
Here are the guidelines that I've tried to follow so far.
- Minimize distance between crystal and MCU
- Match trace lengths for Osc_In and Osc_Out pins on MCU
- Keep load capacitors close to the crystal
- Place ground pour on bottom layer under the crystal
- Create local power and ground for MCU/crystal
After doing the above, I have a few questions.
- Is this an acceptable layout?
- Have I completely missed the mark on any guidelines?
- At 16MHz, should I be putting a guard ring around the crystal?
- Should the load capacitors go between the crystal and the MCU or are they fine where they are at?