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74HC4040N vs. CD4040

Discussion in 'Electronic Design' started by Jerry, Mar 30, 2007.

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  1. Jerry

    Jerry Guest

    The circuit specifies (two off) the latter and I have the former.

    They appear pin-compatible so... is there any reason why the 74HC4040N
    won't substitute for a CD4040?

    The project is a simple EPROM burner with 4040s counting through the
    possible address space.

    Thanks in advance
  2. What voltage is Vcc? The 74xx part is limited to ~5V, the CD4040 will work
    with 15V.
  3. Jerry

    Jerry Guest

    A PS:

    ....I ought to add that I've built the circuit with 74HC4040Ns and (you
    guessed it!) it doesn't work...hmmm. Not unusual I agree but I've
    checked this simple circuit a hundred times, watched the transistion
    of the pulses from a parallel port and nothing but nothing seems to
    trip the Q outputs to the correct states even though the clock and
    reset lines appear to do what they're supposed to.

    Of course, there may simply be a wrong connection/solder bridge/etc
    but AFAIK it's clean and wired as it should be. I've even swapped out
    the 74HC4040Ns for two others (had a bunch of them lying around) but
    to no avail.

  4. Jerry

    Jerry Guest

    5v, the Vpp is derived seperately
  5. Jerry

    Jerry Guest

  6. Aside from Vdd range, the CD4040 is WAY slower at 5V Vdd, and has way
    less drive current capability.
    Sounds like it ought to work unless the designer has done something a
    bit strange-- maybe you should show us the schematic.

    Best regards,
    Spehro Pefhany
  7. Tim Wescott

    Tim Wescott Guest

    What is the maximum voltage reached by the parallel port output pulses?
    CMOS parts need to see voltages close to the power rail, while the
    parallel port is probably assumed to be OK with TTL-level voltages.

    TTL parts into CMOS often works, but it often doesn't -- you should
    check what you're getting, and what the 74HC4040 wants.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at
  8. Werty

    Werty Guest

    Many HC are "new,improved" ...

    HC105 FIFO is improved , you can circulate
    it and still be tri-state ...

    BTW ,,,anyone study Speed-pow pdt ?
    What is the bad stuff ?
    What dont work at 3.3vdc , ultra effecient ?
    Notice the pitfalls , now , on SRAM S-P pdt!
    You can buy SRAM thats less than 1 Mili-W
    per mhz , but you can buy 50 MilliWatt
    from JameCo .

    ? Has anyone got any recent bad experiences.

    Notice DRAM is evolving into PSRAM .
    They have improved DRAM , so much , it
    will kill SRAM .
    It uses about .0001 amps to refresh.

    Im doin ARM , free OpSys . No English ,
    No ASCII , no bloat ( loads at 8KB ) .

  9. Rich Grise

    Rich Grise Guest

    Yeah - at least try the pullups - 4.7K ~ 10K from the reset (pin 11, _STB,
    pin 14 of the port) and clock (pin 10, _AUTLF, port pin 14) lines to your
    own +5V (IC2 OUT).

    Good Luck!
  10. Tam/WB2TT

    Tam/WB2TT Guest

  11. Joerg

    Joerg Guest

    I don't see any decoupling caps in there. If true then that ain't good.
    Place a 0.1uF ceramic next to each chip, shortest possible connection
    from VCC to ground (here it's called VSS). Also one at the output of the
    7805. Might also need a 47uF or 100uF electrolytic at that point but I
    don't know what the parallel port would say to its surge current.

    CD4000 series chips are much slower and they can occasionally live
    without decoupling caps. It's still better to have them. 74HC definitely
    needs them.
  12. Jerry

    Jerry Guest

    Tim: pulses at 5v which, on the clock and reset lines appear to be
    'working' -- ie the reset is pulled low or else is at 5v, similarly
    the clock, but the clock doesn't trip the Qs and the reset doesn't
    reset 'em! (At least, not with any -- excuse the pun -- logic).

    Rich: so put pullup resistors of between 4k7 and 10k across lines
    going to the clock and reset? I'll try it...

    Joerg: no decoupling caps at the moment but I think I can dig a few
    out of my junkbox to try it.

    Thanks everyone. I'll try the above and report back
  13. Werty

    Werty Guest

    Do you still do Taiwan ?

    Im doin a PCB for ARM mcu ,

    prices on STR710FZ2T6 are

    taxed up triple .

    I need to pay $4 , USA wants

    $10 . Quant' 2000 .

    Mine is unique , will be bootable from

    every hardware source , avail' ..

    Drives LCD's , KB's even from the tiny 8KB

    loader ..
  14. Rich Grise

    Rich Grise Guest

    Not "across lines" - from the "clock" pin to +5v, and from the "reset"
    pin to +5v:

    | ______
    clk ----+----| HC4040

    like that, one per each. (the truth is, I don't even know what you mean by
    "across lines" here.)
    I concur on the decoupling caps - locate them as close to the chip as
    possible - I've even mounted them _underneath_ the board, so I can go
    directly to Vcc and gnd, so that the switching noise "spike"(a very
    narrow pulse) has the shortest possible path to go through to get to the
    We'll appreciate the report. :)

    Good Luck!
  15. For some values of "do". I'm just working on getting a couple of
    companies into a partnership for sourcing and supporting some
    specialized high-precision mechanical stuff from there at the moment.
    I have not visited Formosa for a while now. 8-(
    Some semiconductor prices will vary signficantly by geographic
    location, but you can't always be sure they'll be less until you see
    the quotes.
    Try the ROC and the PRC. ST may be dumping parts there and/or the
    price structure may be flatter.

    Best regards,
    Spehro Pefhany
  16. Werty

    Werty Guest

    Some semiconductor prices will vary signficantly by geographic

    Wanna bet !

    ST and Phillips and SamSung

    will be the high volume suppliers of ARM 7 .

    They will be able to price at $4 , if your

    country dont tax them out .

    ATMEL and Intel ,AMD , H.P.

    will lose all .
  17. jasen

    jasen Guest

    this may seem like a stupid question, but do yo have
    Q1 base connected the 7805 output.
  18. Jerry

    Jerry Guest

    Sorry, I'm from Barcelona...

    I can report success though, the project is working after using
    decoupling capacitors and pullup resistors. Many thanks to all here
    who helped -- invaluable!

  19. Oh, for goodness' sake, there's no reason to apologize for where you're
    from! I'm just wondering if you're confident enough with your English
    (Which, by the way, you seem to be writing better than way too many
    Americans these days), to translate what you meant by "across lines",
    or were you just looking for words to express what we generally mean by

    Thanks, and welcome to the loony bin! ;-)

  20. Tim Shoppa

    Tim Shoppa Guest

    I have had difficulties with some brands of 74HC4060's (which are
    similar to but not identical to the 4040).

    In particular, the problem was that in some makers' 74HC4060's, the
    built-in oscillator didn't oscillate reliably. I ended up just specing
    the good old CD4060 which in my particular case does oscillate

    All that said, except for using "analog" sections in digital parts
    (the oldtimes all know that all digital parts are made of analog
    parts!) I've never had a problem when the only power supply was 5V

    Like any digital circuit using counters, you'll want at least some
    bypassing and good construction techniques to make the circuit
    reliable. CMOS (either CD40xx or 74HC40xx) is so much more forgiving
    than regular TTL. And if the original circuit doesn't really work,
    then the transliterated one won't work either :).

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