What I need to do to generate a clock of 1.1MHz

Discussion in 'The Projects Forum' started by redyakuza87, Apr 27, 2009.

  1. redyakuza87

    Thread Starter New Member

    Apr 21, 2009
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    With all due respect,

    I was given a 4060 with crystals 8MHz and I need to generate 1.1MHz with these (and other capacitors and resistors). If I am not mistaken, we can't generate 1.1MHz with that. Hence, the supervisor asked me to use another 4040 connected to the 8MHz output to get 1.1MHz. I am not so sure how it works.

    Any help is appreciated
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Afraid you're not going to get there with an 8MHz crystal and either a 4040 or a 4060.

    A 4040 has /2 (Q1), /4 (Q2), /8 (Q3), etc. outputs, but to get 1.1MHz from 8MHz, you'd need to divide by 7.272... which isn't going to happen.

    A 4060 IC's outputs start at /16 (Q4), so 0.5MHz is the most you could get out of it using an 8MHz crystal.

    If you need a pretty stable 1.1MHz clock, you're going to need to get a different crystal; one that's evenly divisible by 2 to get 1.1MHz would be your best bet.

    If you can tolerate a rather wide variance in frequency, you could go with an RC oscillator. It won't be nearly as accurate as a crystal oscillator.
     
  3. redyakuza87

    Thread Starter New Member

    Apr 21, 2009
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    Thanks..

    That is just what I have in mind as it really is impossible to get 1.1MHz. However, he did say something about connecting the output from 9 of 4060 (the 8MHz output) to 10 on 4040. That is something I have no idea what it is about and what does it do. I hope you can help.

    Thanks again :)
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    What's your tolerance on the frequency?

    I think your boss is thinking that you might get within 1% of 1.1MHz by XORing a number of outputs, but it's going to be ugly, and the clock won't be close to symetrical.
     
  5. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    There's a way of doing it, but you'll need a few more active devices. Take an 8MHZ oscillator, divide by eight to get 1MHz. Divide by ten to get 100KHZ. Remix the 100kHZ with the 1MHZ, and filter. voila.


    Eric
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Double the frequency, and you can use a single flip flop.

    I'd look for a crystal that is already at the freq you're looking for, or are you stuck with the parts you have?
     
  7. CDRIVE

    Senior Member

    Jul 1, 2008
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    Clever! ;)
     
  8. hgmjr

    Moderator

    Jan 28, 2005
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    Do you have any examples of a mixer circuit that would recombine the two squarewaves?

    hgmjr
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Eric is thinking in terms of analog design. Think RF.
     
  10. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Thanks! That's why AAC pays me the big bucks. :D:cool:


    'eric
     
  11. CDRIVE

    Senior Member

    Jul 1, 2008
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    Even if he is it's still doable with square waves.
     
  12. redyakuza87

    Thread Starter New Member

    Apr 21, 2009
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    yes I am stuck with what I have. I am only allowed to use the devices which were listed.
     
  13. thingmaker3

    Retired Moderator

    May 16, 2005
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    Pity no diodes were allowed... one could make a divide-by-seven counter with a triplet of diodes and a pull-up resistor.
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    If you connected the 4060, 4040 and crystal up like your instructor suggested, then you could use 4070 XOR gates wired to the Q3, Q7, Q8, Q11, Q12 and Q14 outputs to approximate 1.1MHz. The clock wouldn't be symmetrical, but it would average out over time to be within 1% of 1.1MHz.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    See the attached schematic.

    Vdd/Vss connections to the ICs and supply bypass capacitors are not shown.
     
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