Componant equivalent

Discussion in 'General Electronics Chat' started by arthur92710, Feb 14, 2008.

  1. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
    can the SN74160 BCD Decade Counter IC replace the 4017? Their both decade counters so i think it should. There for my binary clock.
    Thing is that mouser sells the 4017 for $.5 each and on ebay theres a stor that has the 74160 for $.18 each. Thats a big difference!
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    A 74160 is old TTL, while the 4017 is CMOS. It would be awkward to try to combine those logic families. TTL has to have no more than 5.4 volts feeding it, and uses more than ten times the power of CMOS. You have to use pullup resistors on unused inputs, noise margins are tiny, and there is a very small selection of remaining logic available in TTL.

    As long as you keep Vcc at 5 volts, you can mix 74HC160's in with CMOS - HC is CMOS with TTL functions. Check Jameco for prices.
  3. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
    Jameco has some for .17 but there out of stock. Thanks but I think i found a guy on ebay that has some good deals, $10 for 100 parts 25pc of 4chips. thats .10, but he does not post shipping info so I will contact him.

    Thanks for reminding me that the the TTL is a power hungry chip(well hungrier then the cmos)
  4. SgtWookie


    Jul 17, 2007
    It's not only that TTL is power hungry and voltage-finicky (4.75-5.25), the levels are much tighter. You can run 54-series (mil-spec) from 4.5 to 5.5v, the 74 series require the tighter specs. You would need to make driver circuits for your CMOS ICs to be able to "talk" to the old TTL ICs; they wouldn't have enough current to drive TTL inputs.
  5. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    Logic levels can be different, even for the same Vcc.

    For instance, you can use HC (CMOS) to drive HCT (CMOS-TTL), but not the other way around. It's not wise to use HCT devices for driving HC, not that it can't work at all, but it's not a reliable thing to do because the Hi/Lo logic transition levels are not compatible.