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BCD to hexadecimal 7 segment LED driver

Discussion in 'Electronic Components' started by Eric, May 5, 2005.

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  1. Eric

    Eric Guest

    Once upon a time in the 70's Motorola came out with a
    BCD to hexadecimal 7 segment LED driver in the MC144xx series,

    Instead of displaying rubbish characters between binary input 1010 to 1111
    it displayed hexadecimal A to F

    But wait that is not all, it did not need 7 limit resistors, that so many
    (all) other "BCD to 7 segment LED drivers" need,

    Every time I see a circuit that uses "BCD to 7 segment LED driver" in it
    there are also the other 7 resistor there too,

    I thought it was great I used a few, I wonder why they never took off
     
  2. Hmm. Are you sure you're not conflating the DM9368 driver chip from
    Fairchild vs. the Motorola MC14511 (which is a CMOS chip with NPN
    emitter-follower bipolar drivers, and does require current limiting
    resistors)? That's the only one that I can recall that decoded hex,
    and it also had the constant current outputs of which you speak.

    The reasons probably had to do with second sources, price and
    availability. That's why we never used them. OTOH, there's a 4511 in
    each of our mass-produced CO detectors we have at home.


    Best regards,
    Spehro Pefhany
     
  3. Tim Shoppa

    Tim Shoppa Guest

    LED driver in the MC144xx series

    MC14495 is I think what you're writing about.

    The Fairchild DM9368 is still out there and does hex too.

    TI and I think HP also had LED displays with on-display hex
    decoders/drivers.
    There are lots of LED driver chips from TI/Allegro/Micrel which have
    constant current drivers on the chip. They do not do hexadecimal
    decoding, their input interface is simply a bit-per-segment shift
    register, this works great with modern microcontrollers, you simply
    have a little lookup table in your program to produce the desired
    display.

    A bit older (but I think still available) is the MM5450 for LED
    driving.

    The Motorola MC14499 put a four-digit seven segment multiplexed driver
    into a single 16-bit DIP, with a serial interface for data in. But it
    didn't do hex.

    Tim.
     
  4. Mark Zenier

    Mark Zenier Guest


    They were obselete not long after their introduction. After
    the late '70s, just about everything with a display used a
    microprocessor.

    Jameco probaly still has them. At only two or three times
    the price of a PIC.

    Mark Zenier Washington State resident
     
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