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SourceTwo

Expert Boarder 		Click here to see the profile of this user

2008/02/20 09:17

Crystal options

Dear Luminary,

So far, I have used an 8.000MHz 5mm x 7mm crystal for my Luminary designs, however, I have been salivating over some of the smaller crystals available. Unfortunately, the 8.192MHz upper limit of the PLL selection field limits ones choice of crystals to the bulkier variety.

Is there any plan to permit higher frequency crystal options in the future? It would sure be nice if we could go as high as 16.000MHZ, but even 12.000MHz would open up a few of the smaller-sized options.

I realize the benefits of using a lower frequency crystal from an EMI perspective, and appreciate the present capability from that regard. It's just the crystal is bigger than the processor...

Hope you can comment. Thank you!

Regards,
Dave

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matten

Fresh Boarder 		Click here to see the profile of this user

2008/06/26 08:27

Re:Crystal options

It also seems odd that it is always necessary to add a second crystal for the Ethernet controller. Given that many people will want to have their system clock at the maximum frequency of 50MHz, an option to clock the Ethernet controller from a divide-by-2 of the system clock would seem very useful. Or is the PLL not stable enough for Ethernet?

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PJE

Senior Boarder 		Click here to see the profile of this user

2008/07/14 10:12

Re:Crystal options

I was looking on Digikey, and NDK has a 5x3.2mm 8MHz XTAL which seems to be the same physical size as the 25MHz XTAL used for the Ethernet on the Luminary Eval boards...

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=644-1132-1-ND

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SourceTwo

Expert Boarder 		Click here to see the profile of this user

2008/07/14 13:27

Re:Crystal options

Hi PJE,

Nice find! I had moved to a 6mm x 3.6mm http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=535-9628-1-ND, but see that yours is even smaller, although a bit more expensive. The size difference could be a benefit to me down the road. Thanks again!

Regards,
Dave

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cb1

Platinum Boarder 		Click here to see the profile of this user

2008/07/14 16:43

Re:Crystal options

Guys-

This is great - thank you both.

As I demo our 48 pin LMI with the old xtal TOWERING over AND bigger than the micro - how embarrassing!

No more - thanks much...

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rocksoft

Expert Boarder 		Click here to see the profile of this user

2008/07/28 16:54

Re:Crystal options

If space is more important than price...

I use these oscillator modules and they work fine for both processor and ethernet.

EPSON TOYOCOM SG-310 SCF C - 8 and 25MHZ

3.2 x 2.5mm, quite small.

Regards,

Liam.

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