Req: Help needed to design a oscillator

[madhan7710]

Hello,

Am developing a project and the main decoder ic requires 27mhz clock input(not crystal). It operates at 3.3v and that's the maximum VCC.
the problem is i couldnt get a 27mhz oscillator in my area. am able to get 27mhz crystal though. could anyone share a oscillator circuit that works with 27mhz crystal and 3.3v VCC so that i can feed the output directly to the ic.

I searched the net and i could get some 74 and 40 series ic based oscillator but it couldnt take 27mhz crystal directly itseems also VCC is higher.

hope someone must have a solution...

thanks in advance.

[solutions]

http://www.idt.com/document/mk2727-datasheet

[krepa]

One transistor and some R/C is OK with you?
Then you can try http://www.rakon.com/Products/Public%20Documents/Whitepapers/SINGLE%20TRANSISTOR%20CRYSTAL%20OSCILLATOR%20CIRCUITS.pdf
There are several circuits which are also explained.
Actually if you need full Vcc swing you need to amplify it so may it's not so good idea.



Posted on: June 24, 2012, 03:41:10 15:41 - Automerged
Another option - if you like SMT is to buy ready made ocsillator http://in.element14.com/jsp/search/browse.jsp?N=2103+204350&Ntk=gensearch&Ntt=27MHz&Ntx=mode+matchallpartial
Maybe you can get also DIP/DIL vesion from other supliers (digikey,...)

[madhan7710]

Thanks for the reply's. At last i ordered the 27mhz module itself as i couldn't get 74hc04 to work properly with 27mhz crystal.

[solutions]

The module you said you couldn't get?

What are you using now?

[madhan7710]

I got a contact of crystal and oscillator manufacturer detail where any custom made frequency is possible but very costly for small quantity. I placed order for 10 Nos there and got it for testing and also ordered a cheaper item in mouser(still didn't reached my hand).

[solutions]

Who, where, and how much for 10? This is not just for me, because I don't need it now. Someone may need it in a search and it'd be nice to have that info available here

[DreamCat]

74HCU??

[krepa]

Who, where, and how much for 10? This is not just for me, because I don't need it now. Someone may need it in a search and it'd be nice to have that info available here

One manufacturer from Czech Republic. They can do custom frequencies. It is not cheap but it is possibility.
http://www.krystaly.cz/en/

[Zorktronics]

    Have you done a solution to this problem?

    It's not the easy way, but you can design your own crystal oscillator, i recommend the book: Foundations of oscillator circuit design, from Guilhermo Gonzales, it was helpful when i had to design some Colpitts oscillators, this book is only a start, a lot of nonlinear simulation will be necessary.

    Besides that, you'll need to do spice simulations and get reliable transistor models, maybe you will need to do an amplifier to have the right voltage level to drive your logic buffer.
   
    If you need more specific advice please reply on this topic.

   Good luck!