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Erik Friesen
03-23-2009, 10:33 AM
I need a nice 5 mhz sm crystal. Most are clunking hulks that are basically cans on a plastic base with the legs splayed out. Has anyone found some nice ones?

Phil Pilgrim (PhiPi)
03-23-2009, 10:56 AM
No. I've looked high and low for one, to no avail, and had to settle on a 10MHz unit for a recent design. If you ever find one, please let us all know!

-Phil

Beau Schwabe
03-23-2009, 11:08 AM
ICM - International Crystal Manufacturing (http://www.icmfg.com/)· ... Is local to me and I have done business with them in the past for some custom cut precision crystals.· I will give them a call tomorrow and see what they might offer in the way of pricing.· Since our crystals were custom cut, it did cost more than their standard crystals, but all the same their·prices seemed to be reasonable.



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Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

Leon
03-23-2009, 02:04 PM
5 MHz crystals are simply too large for most small SM packages. ACT can supply quite small ones:

http://www.actcrystals.com/

Leon

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Post Edited (Leon) : 3/23/2009 6:14:56 AM GMT

virtuPIC
03-23-2009, 02:11 PM
Mouser also has crystals (http://de.mouser.com/Search/Refine.aspx?N=5115911+4294622341&Keyword=crystal&FS=True) in several different packages in stock. Also look at Digi-Key (http://www.digikey.com). Unfortunately, they currently don't have any 5 MHz crystals available.

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Timothy D. Swieter
03-23-2009, 02:40 PM
I am doing a design at the moment with an NDK 10MHz. crystal: parts.digikey.com/1/parts/1387628-crystal-10-00-mhz-8-0-pf-smd-nx5032ga-10mhz-w.html (http://parts.digikey.com/1/parts/1387628-crystal-10-00-mhz-8-0-pf-smd-nx5032ga-10mhz-w.html) Also in the past I used a 10MHz. crystal from Fox: search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=631-1030-1-ND (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=631-1030-1-ND). On the Fox crystal, be sure to triple check the footprint and note the orientation in the data sheet of front and back of the part. I messed up a board run because I only double checked and I misinterpreted the data sheet.

I also agree with Phil in that I looked high and low too. I am not an expert in this realm, but I did a lot of searching. What would be the advantages or disadvantages to using a 10MHz. crystal and PLL8x versus the 5MHz. cyrstal at PLL16x (both system speeds of 80MHz.)? In the past I think this topic was discussed extensively, especially in the Hydra forum.

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RizThomas
03-23-2009, 04:11 PM
hello
just picked up the last 3 stocks locally. They are twice the height of the one on the protoboards and are
marked 18pf. They seem to work but not so sure.
Any comments please

Leon
03-23-2009, 07:29 PM
The frequency will be off slightly due to the different load capacitance, but it probably won't matter.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Erik Friesen
03-23-2009, 08:05 PM
There are some decent 10mhz at mouser. That takes it out of parallax specs technically, not?

Peter Jakacki
03-23-2009, 09:22 PM
These aren't SM but they (or similar) have been mentioned before on this forum. Look for CSA309-5.000MABJ-UB, Mouser has plenty at $0.78 1 off. They are 8.8mm x 3mm and take up less room than your standard SM HC49/4. As for purely SM crystals there certainly are some tiny little ones but $$$ and hard to get.

Perhaps Prop II will have a high-speed trimmed RC oscillator :) That would be nice.

*Peter*

Erik Friesen
03-23-2009, 09:26 PM
The issue I have is that I have a transflective lcd pasted on the opposite side of the board. I have used the little cans before, and I could use them here, but I would have to make sure that the leads wouldn't go past the bottom. Do you think that the cases on these could be soldered to the board without causing operation issues?

Peter Jakacki
03-23-2009, 10:19 PM
I'd treat the leads as SM leads rather than TH but the can is normally too sensitive for soldering. You can however use rubber adhesive on the end of it to secure it to the pcb.

*Peter*

Chad George
03-24-2009, 02:51 AM
I've used these in the past:

search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=300-8121-1-ND (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=300-8121-1-ND)

There's also a CS10 version that's quite a bit smaller, but I don't think they have it in 5Mhz.

Nick McClick
03-24-2009, 03:07 AM
re: 5Mhz vs. 10Mhz. I asked that question on the Hydra Forums (http://forums.parallax.com/showthread.php?p=738992) a while ago.

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Beau Schwabe
03-24-2009, 07:09 AM
I called ICM this morning, and what they have is comparable to what we already offer. They have a smaller height surface mount option, but it has a slightly larger footprint, also in this size, the frequency offered is just over 8.3MHz ... a 5MHz option is not available.

For kicks anyway, I asked them to send me a price-break quote to see if there was any advantage to our current crystal options. So far I have not heard back from them.

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Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

Chris_D
03-24-2009, 07:40 AM
I am curious as to why there isn't the pursuit of an 80 Mhz xtal?· Why is it that 5 Mhz is used with PLL multiplier, and not simply using an 80Mhz.· I am sure there is a good and obvious reason, but being electronics challenged, I don't know why.



Chris

Beau Schwabe
03-24-2009, 08:07 AM
Chris_D,

Cost is one factor. Another factor is the amount of RF radiation you now have "external" to the chip that might affect other devices nearby. It's better to do this internally if you are able to.

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Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

Rayman
03-25-2009, 12:40 AM
If you're driving an LCD screen and don't need to put out NTSC, then I think one of the FOX oscillators would work just as well and they come in small SMT packages... I got sampled some 100 MHz ones for free from them...