Connect with us

74c14 substitute follow up

Discussion in 'Electronic Repair' started by yhan, Mar 29, 2006.

Scroll to continue with content
  1. yhan

    yhan Guest

    sorry for reposting. I just added some information about voltage rating
    of two ICs.
    according to :

    Yes, you can. It's the number 7414 which tells the purpose of the chip.

    The C-letter means it is cmos-type (and it needs to be in your circuit,

    as you mentioned), and H means it is high-speed-type. It is not
    mentioned to be necessary in your circuit, but it is ok to use the
    high-speed type, although not necessary.

    Both ones are inverting. There are mistake, or maybe the maker of the
    datasheet of the 74C14 has considered the "invertingness" a "special
    feature" which wouldn't be necessary to tell on the header.

    Reply Rate this post:

    From: Gerard Bok - view profile
    Date: Tues, Mar 28 2006 5:16 am
    Email: (Gerard Bok)
    Not yet ratedRating:
    show options

    Reply | Reply to Author | Forward | Print | Individual Message | Show
    original | Report Abuse | Find messages by this author

    While you are right with the 'general picture' that it is the
    function that counts, you may well be wrong here :)

    Use in a C-meter, as the poster mentioned, is likely to be
    dependant on the Schmitt trigger's threshold.
    And that is one of specs that varies between different
    technologies :)

    Kind regards,
    Gerard Bok

    thanks to replies. According to the datasheet the VCC of of C is higher

    than HC part. In the capacitance meter i am planning to make, its
    supply voltage is 12 volts but 74hc14n VCC pin max is 6 volts only.
    That might be the problem. With the transistor tester using also 74c14,

    its supply voltage is 6 volts. In this case, the 74hc14n might be
    suited as substitute but not in the capacitance meter with the supply
    voltage of 12 volts. (Because 74c14 has a Vcc ranging from 3.5-15 v but

    74hc14n only up to 6 volts). Am I right?

    tnx again,

  2. Guest

    Okhay, if that is said on the datasheet and ur circuit is using 12V,
    you're right, that it is a problem, too, although you can correct it by
    using a 7805 regulator to drop down the Vcc to 5V. But, the problem
    that Gerard Bok mentioned refers to _threshold_ voltage. It may cause
    problems if it is different, depending on the circuit. See datasheets
    if the threshold voltages are mentioned there. But even if not, you can
    try it if you want. But if u do, remember to use the regulation for Vcc!
  3. yhan

    yhan Guest

    thanks for the support, ill try it soon...
  4. yhan

    yhan Guest

    good day, let me ask more question please.

    I have here 7805 regulator ready for use. I just dont understand if a
    12 volt circuit design can be operated on 5 volts. Let me enlighten
    with this thing. Can it be compatible? Is there no operating
    differences or malfunction of the circuit because the circuit will
    operate with lower voltage supply and that might affect the operation
    because it doesn't go with the circuit design? If it is still works,
    i'll be glad coz i will not bother to find 74c14 which is not available
    in my place.

    tnx again,

  5. James Beck

    James Beck Guest

    I would stick with the original design and get the C parts. The higher
    operating voltage may be needed for a particular function of the device.

  6. Mike Berger

    Mike Berger Guest

    Unless it's a purely digital circuit (and possibly even
    then) the different voltage level will definitely affect
    its operation. Find the proper chip.
  7. Guest

    I'm very sorry, I was quite careless. Like someones already mentioned,
    it won't work (and actually the chip will burn) if the signal levels
    are too high, even though u used proper dropping at the Vcc. You may
    never use higher signal level than specificated...
  8. Well, actually you can interface 12V CMOS to 5V TTL if you use current
    limiting resistors between the two familys. For example you can have a
    12V high/low feeding into a TTL input if you put a 1.2K resistor in
    series so the input protection diodes will not be blown, you can output
    TTL to 12V by using open collector buffers - these (7416s for example)
    can handle up to 15V with proper design.

    Back in the early days MOS (17V) circuits would be directly interfaced
    to TTL by some clever power supply design - split the 17 supply to
    +5/-12 with the TTL running on the +5 section, then use resistors to
    interface the two families. Look for Gottlieb System 1 MPU schematics
    for some ideas.

    Don Lancaster's CMOS Cookbook covers this TTL/CMOS as well, and I think
    the TTL Cookbook mentions interfacing as well.

    John :-#)#
    (Please post followups or tech enquires to the newsgroup) John's
    Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
    (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) "Old pinballers never die, they
    just flip out."
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day