+ Reply to Thread
Results 1 to 9 of 9

Thread: logic output HIGH from 5V to 12V

  1. #1
    bogdanfirst Good bogdanfirst Good
    Join Date
    Dec 2002
    Location
    Ramnicu Valcea, Romania
    Posts
    1,316

    Default logic output HIGH from 5V to 12V

    hello!
    i got a circuit that outputs logic signals wich have the HIGH of 5V, there are some 74HC CMOS circuits. the problem is that i want the circut to drive some other devices, but those require that i have a 12V output for H and 0V for L.
    how could i do that without use of transistors?
    could a Schmitt trigger buffer do the job?
    if so, wich should i use?


  2. #2
    Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent
    Join Date
    May 2003
    Location
    Idaho, USA
    Posts
    6,723

    Default

    Take a look at CD40109.

  3. #3
    bogdanfirst Good bogdanfirst Good
    Join Date
    Dec 2002
    Location
    Ramnicu Valcea, Romania
    Posts
    1,316

    Default

    well, it is good, but now quite like i need. i checked a datasheet i have and there is somthing i dont understand. it says that for a HIGH leven input voltage for VDD=15V, 11V are needed. so will it work if i apply 5V ? as H ?

  4. #4
    sbayeta Newbie
    Join Date
    Jul 2003
    Posts
    40

    Default

    What's the problem with transistors ? Why are you trying to avoid them ?

  5. #5
    bogdanfirst Good bogdanfirst Good
    Join Date
    Dec 2002
    Location
    Ramnicu Valcea, Romania
    Posts
    1,316

    Default

    well, first, i will have to use 2 transistors for each bit, because a transistor inverts the signal.
    then, i have 24 bits * 2 = 48 transistors, so they will be a lot more xpensive than using 3 ic's with 8 buffers, or 4 ic's with 6 buffers.
    so the circuit will be a lot harder to build, morre expensive, more time consuming, and more space consuming.

  6. #6
    Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent Roff Excellent
    Join Date
    May 2003
    Location
    Idaho, USA
    Posts
    6,723

    Default

    Quote Originally Posted by bogdanfirst
    well, it is good, but now quite like i need. i checked a datasheet i have and there is somthing i dont understand. it says that for a HIGH leven input voltage for VDD=15V, 11V are needed. so will it work if i apply 5V ? as H ?
    I have not used this part, but the way I interpret the datasheet, the input logic threshold is first order dependent on VCC (Vth ~ VCC/2), and only slightly dependent on VDD. See the bottom of the table "Static Electrical Characteristics", and Fig. 9. Neither figure explicitly specifies the behavior with VCC=5v and VDD=12v, but the table "Dynamic Electrical Characteristics" does have timing specs for VCC=5v, VDD=10v and for VCC=5v, VDD=15v, so You should expect it will work for VDD=12v.

  7. #7
    olly_k Newbie
    Join Date
    Jul 2003
    Location
    UK
    Posts
    166

    Default

    well, first, i will have to use 2 transistors for each bit, because a transistor inverts the signal.
    well that depends whether you use an npn or pnp or FET and how you connect it! It is wrong to say it will invert the signal tell us more about the interface etc and we can help!
    OLLY_K

  8. #8
    sbayeta Newbie
    Join Date
    Jul 2003
    Posts
    40

    Default

    Quote Originally Posted by olly_k
    well, first, i will have to use 2 transistors for each bit, because a transistor inverts the signal.
    well that depends whether you use an npn or pnp or FET and how you connect it! It is wrong to say it will invert the signal tell us more about the interface etc and we can help!
    Right, and you didn't say 48 signals

  9. #9
    bogdanfirst Good bogdanfirst Good
    Join Date
    Dec 2002
    Location
    Ramnicu Valcea, Romania
    Posts
    1,316

    Default

    Ron, it is exactly as you say that i understand from your datasheet. the problem is the datasheet that i have.....that confuses me.
    but still, i have found a circuit in a book that uses this IC just for what i need. so i don't think there will be a problem to use it as i want.
    thanks for the help....
    yet, are there any other similar IC's. maybe some that don't have the enable pins, and are 2 state, not 3 ? an possibly contain more than 4 shifters?
    i'll take a look too.

+ Reply to Thread

Tags for this Thread