Is this an appropriate crystal?

[Dan East]

[EDIT] Skip to my next post [/EDIT]

The datasheet says to use a parallel cut crystal, however this retailer does not specify if this crystal is parallel or series cut:

**broken link removed**.

Would that crystal work with a PIC?

Also, anyone recommend other online retailers for 20 MHz crystals? I hate to pay $5 to ship something with virtually no weight. I would also prefer the low-profile case, which Jameco does not offer at 20 MHz.

Thanks,

Dan East

 

[Dan East]

Shoot, after looking at that page for the 4th time I finally see that it is series cut.

Any recommendations for an online retailer for 20 MHz parallel cut crystals in very small quantity (<5)?

Dan East

 

[Dan East]

Okay, let me take a step back.

I've read on this forum and in other documentation that everything from trace length to trace thickness affect crystal performance. As this is all far beyond me, am I safe using a 20 MHz crystal and matching caps, when I don't have the skill to properly design a PCB to take into account all the nuances?

Or should I just stick with an oscillator? The downsides I see are higher power consumption, larger size and expense.

Thanks!

Dan East

 

[Nigel Goodwin]

I've read on this forum and in other documentation that everything from trace length to trace thickness affect crystal performance. As this is all far beyond me, am I safe using a 20 MHz crystal and matching caps, when I don't have the skill to properly design a PCB to take into account all the nuances?

Just bung a crystal and two capacitors on the correct pins, the layout doesn't have any effect at these sorts of frequencies - within reason!.

The capacitors are also extremely uncritical, anywhere between 10pf and 33pf will be absolutely fine! - it's really a lot easier than you are thinking!.

If you're still at all worried about layout, try looking at the veroboard layouts in my tutorials - the 16F876 and 16F877 boards both use 20MHz crystals - they work perfectly.

 

[laroche73]

Xtals

This may help answer some of your questions about oscillators (scoll to p.8 ). I agree with Nigel, circuit values are not too critical at these frequencies, you'd have to work hard not to make the crystal oscillate.

 

[Dan East]

Here's the oscillator portion of my board. I'm using a PIC16F628 even though the part is labeled otherwise.

Dan East

 

[Nigel Goodwin]

Here's the oscillator portion of my board. I'm using a PIC16F628 even though the part is labeled otherwise.

That looks perfectly fine!.