50 Mhz Crystal Recommendations

Brody

Hi, I have been having some difficulty getting a good 50MHz crystal for my SX20 project. I just ordered one from Mouser a week ago, but it isn't working properly. I varied up the capacitance and the clock settings in the source code. I am assuming I purchased the wrong type of crystal.

Does anyone have any Mouser or Digikey part numbers for a 50MHz crystal that definitely works?

How about any 50MHz ttl oscillators that definitely work?

Thanks

Bean

Brody,
Does it HAVE to be a crystal ? I use the 50MHz resonators from parallax and they work fine.

Leaded = http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/resonator/List/0/SortField/4/ProductID/360/Default.aspx
SMT = http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/resonator/List/0/SortField/4/ProductID/349/Default.aspx

Bean.

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Brody

Thanks Bean.

Right now I have a stack of the 50MHz resonators and they seem to work well.

I have two main issues though. I am using an SX20 in two different devices. Both require time-sensitive operations. One of the devices is powered from a wall wart. The other is battery powered. For the device from the wall wart I actually purchased a 50MHz oscillator, and that works amazingly.

For the battery powered device I need precision and low power. Plus the PCB layout is already on the way to the fab and I assumed the HC-49 50MHz crystal would work without a hitch. I may have hooked it up incorrectly, but it seems that the data sheet is specific about the type of 50MHz crystal that can be used with the SX chips.

I guess it doesn't have to be a crystal, but it would be best in my current situation.

Thanks again.

Brody

I found this page to be helpful. I will check out the recommended crystals:

www.sxlist.com/TECHREF/ubicom/clocks.htm

PJAllen

The crystal must be of the parallel resonant sort.· That's in the SX20-28 v1.6 data sheet.

9.0 Oscillator Circuits

9.1 A parallel resonant crystal type is recommended. Use of series resonant crystal is not recommended.

Fig. 9-1 shows the model crystal timebase circuit

Table 9-2 shows support component C,R values.

Brody

I read that part. My real difficulty is in finding a 50MHz fundamental crystal. They used to make a few in the through-hole mount, but I could only find surface mounts that I could buy in single quantities. I may go this route.