Generate a square wave using crystal

Discussion in 'General Electronics Chat' started by dumindu89, Sep 1, 2012.

  1. dumindu89

    Thread Starter Member

    Oct 28, 2010
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    I need to get a square wave and voltage levels are similar LVTTL input levels using a crystal.

    How can I do this? what is the easiest way?
     
  2. #12

    Expert

    Nov 30, 2010
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    Use an LVTTL IC with inverting amplifiers in it, like a quad NAND.
     
  3. dumindu89

    Thread Starter Member

    Oct 28, 2010
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    But it doesn't include a crystal. Isn't it?
    I need to use a crystal because I need a higher stability and accuracy in the square wave.
     
  4. #12

    Expert

    Nov 30, 2010
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    Last edited: Sep 2, 2012
    absf likes this.
  5. ramancini8

    Member

    Jul 18, 2012
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    Intersil make an IC that just needs a crystal to be a square wave oscillator.
     
  6. Dodgydave

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    Jun 22, 2012
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  7. panic mode

    Senior Member

    Oct 10, 2011
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    use crystal oscillator then run the signal through gate with Schmidt trigger. it will square it even if input was sine wave. if you want 50% duty cycle, add flipflop. there is tons of circuits that produce signal you require. if the frequency need some adjustment, use PLL chip.
     
  8. dumindu89

    Thread Starter Member

    Oct 28, 2010
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    Can you explain bit more?
    Yeah. I need a square wave with 50% duty cycle.


    I implemented the circuit shown in the following figure which is designed for TTL. It worked fine with TTL 7404 IC.

    [​IMG]

    Link to the web page: http://www.eleccircuit.com/crystal-oscillator-using-ttl/

    But it didn't work with the NOT gates implemented using the Altera MAX ii CPLD (LVTTL). :(
    Any suggestion to make it work with LVTTL? Is it possible to make it work with LVTTL by changing the R1 and R4 values?
     
  9. dumindu89

    Thread Starter Member

    Oct 28, 2010
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    All the circuits are designed for TTL devices instead of LVTTL. The previous one which is designed for TTL is didn't work with LVTTL. (refer the previous post). Will these circuits work with LVTTL?


    Guys!! Any Idea please?
     
    Last edited: Sep 27, 2012
  10. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Use a CD4069 chip it will work on 3 v, or use a a LVTTL
     
  11. dumindu89

    Thread Starter Member

    Oct 28, 2010
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    Will those designs work with the NOT gates implemented on a FPGA which has LVTTL?
     
  12. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    As i have never worked on FPGA's , i cant give you an answer, i can only assume if they have inverter gates separate to the chip, they may work, try it and find out.
     
  13. ramancini8

    Member

    Jul 18, 2012
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    I believe this circuit needs a series resonant crystal.
     
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