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Looking for >5V pretty fast logic

Discussion in 'Electronic Design' started by Klaus Kragelund, Nov 22, 2007.

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  1. Hi

    I am using a CD4093 with 4 schmitt triggers wired as a free running
    oscillator supplied by 10V. The CD4093 is 4000 series CMOS logic, but
    it is just too slow for my application (need a 3MHz oscillator/VCO). I
    can live with trigger level that has high tolerance and would shift
    the frequency since the loop is closed to form a VCO

    So been looking at the 74HC and other series, but cannot find anything
    that can handle more than 6V and that is fast

    Do any of you guys know of a chip? Or perhaps a faster VCO than the
    CD4046 PLL. Alternatively building a astable oscillator with 2
    MOSFETs. Maybe even a 74HC 5V IC, but with a simple levelshift to get
    a fast 10V output

    Regards

    Klaus
     
  2. John Fields

    John Fields Guest

     
  3. Good suggestion. The problem is I need it to have low current
    consumption and that is difficult to find when it needs to be fast
    also (<100ns response)

    Right now it looks like a LMC555 can do the trick

    Thanks

    Klaus
     
  4. john jardine

    john jardine Guest

    The 'HEF' Cmos (eg HEF4093) is twice as fast as the normal stuff.
     
  5. Joerg

    Joerg Guest

    Klaus, check out this one:

    http://www.national.com/ds/LM/LM5112.pdf

    John Larkin had recently used it in a switcher. Unfortunately it's
    around $0.50. Other than the CD4000 series there isn't much anymore that
    could run at high voltages. 74HC is usually rated up to 6V.
     
  6. Jim Thompson

    Jim Thompson Guest

    Joerg, Nice part! You really ought to find some clientele who can
    afford 50¢ ;-)

    ...Jim Thompson
     
  7. Joerg

    Joerg Guest

    Oh, they all could. But it doesn't always make sense since many designs
    are very high volume. Right now I am "discretizing" an IC design because
    the trusty old parts might go unobtanium soon and nearly all the
    newfangled chips that could replace it are north of two bucks. Heck, we
    can get a good bottle of Merlot for that. Ok, I know you don't like the
    Shaw brand ;-)

    BTW, for the record, it wasn't me but it was John who brought this part
    to our attention a few months ago.
     
  8. Jim Thompson

    Jim Thompson Guest

    Good ol' Upchuck ;-)

    Here's my latest favorite Chardonnay... Kim Crawford "unoaked"... $13
    Thanks, John! I need such parts to convince clients to stick with a
    cheap low-voltage process for the main chip and use interface-specific
    parts at the loads.

    ...Jim Thompson
     
  9. Joerg

    Joerg Guest

    Our favorite winery is this one:

    http://coulsonwinery.com/wine_list.htm

    Had a Sangiovese yesterday, bottled it ourselves back then. That was a
    lot of fun. Unfortunately Ed (seen in the picture) has passed away :-(

    That was not what National's marketeers intended the part to do ;-)
     
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