PIC18F4550 Crystal Oscillator PCB layout?

[Tom-H-PIC]

Hello All
Is it a good idea to use a ground plane around the crystal and capacitors?
Thanks All
Tom

[PCM programmer]

See Newguy's post about half-way down this thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=25592

[Tom-H-PIC]

Thanks PCM programmer and Newguy!
That was what I was think would be an issues with putting the ground plan around the crystal.
I was looking at some of the Microchip boards that I have and they did not have a ground plan but all of the things that I have read say that a ground plan around the crystal is a good idea and even some manufactures recommend it.
So thanks for that first hand experience Newguy and thank you for pointing out that post PCM programmer. I did not find it when I searched.
Tom

[Ttelmah]

There used to be a standard layout, with a gound 'block' running under the crystal itself, and a 'loop' round the connections, but not going too close to the actual pins. The block commonly had two pads to allow a tie to go round the crystal when high mechanical forces are present. Modern smaller crystals, and especially SM types, are normally laid out with a gap in the top side power plane round this area, and also taking care to not route other signals close to the actual oscillator pins. Most manufacturers do recommend a ground plane below the crystal on the other side of the board. Some components with low power oscillators, have the pins each side of the oscillator connections 'NC', and you are meant to put a protective ground 'ring' through these, round the entire oscillator area. Some components recommend a 'ground island' under the oscillator separate from the main ground plane. A ground plane, reduces the risk of signal pickup, which can be a significant problem given the gain of the oscillator, but neds to be done with care ifthe capacitance is not to introduce problems as already mentioned. I tend to use a protective ring, and this is a petty safe option to use.

Best Wishes