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High voltage line drivers

Discussion in 'Electronic Design' started by David, Sep 23, 2006.

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  1. David

    David Guest

    Can someone suggest a high voltage line driver IC? I have requirements
    for two seperate uses.

    1.) High voltage input. The IC needs to receive 0-30V digital input
    voltages and output 5V logic levels. However, I still want the driver
    to work if the input voltage levels are only 0-3.3V.

    2.) High voltage output. The IC needs to receive 5V digital input
    voltages and output 30V digital equivilents.

    Thanks,
    David
     
  2. mkaras

    mkaras Guest

    For the 1) application get your hands on the old style RS232 receiver
    of the 1488/1489 set. The DS1489s inputs work up to +/- 30V.

    For the 2) driver take a look at the SN75452 type parts. These can
    handle up to 30V on the outputs. (Both Digikey and Jameco have them in
    stock).

    These are older parts so I would encourage you to look at other lower
    voltage transmission techniques if you are intending to go into
    production with the thing you are trying to design/build.

    - mkaras
     
  3. Do you need the receiver to automatically center its threshold right in
    the middle?
    How far does the signal have to go? At what data rate? Does it have
    to be short-circuit protected? What about static protection?



    Your basic LM339 comparator IIRC can be used for both jobs if the
    requirements arent too tough.
     
  4. David

    David Guest


    Interesting idea. I'll have to investigate.


    I've thought about open collector solutions, but I was hoping for push
    pull.


    I do intend to enter production. It is an industrial control application
    that needs to interface with PLC's. I'm no PLC expert, but I believe
    they typically have 24V digital I/O. That is why I need the high
    voltage.

    However, I also want the device to be usefull on a lab bench where 3.3V
    logic is prominent. That is why I need the large range of logic
    voltages.

    Thanks,
    David
     
  5. David

    David Guest


    This would be a great feature, but not absolutely required. It would be
    acceptable for the vIL_MAX and vIH_MIN to remain constant as long as
    they worked from 3.3V logic all the way up to 24V logic.


    This is an industrial control product that will interface to PLC's which
    typically operate at 24V. The transmission distance can become very
    long. Data rates will be slow. Maybe 100ns to 200ns risetimes. Short
    circuit protection is very desireable as well as at least 2KV static
    protection.


    That is a very good suggestion. That may be exactly what what I need.
    What is a typical switching time for a comparator that is saturated at
    the rail?


    Thanks,
    David
     
  6. JoeBloe

    JoeBloe Guest

    There is at least one problem with what you need. To rise to 30
    Volts can be said to be easy. To do so with digital data, a factor
    known as slew rate weighs in. You won't be able to go very fast
    before the slew rate issues corrupt the data, limiting the rate you
    can pass data at. Are such chips even around?

    It is sort of akin to "floating" ones valves out from revving an
    engine to high for the weak valve springs. Motor can only turn so
    fast.
     

  7. Whoa, Nelly! Sending 100nsec risetime signals any distance is going
    to require using differential twisted-pair or coax. For the
    twisted-pair you'll need some strong differential drivers, for the coax
    some 50 or 75 ohm drivers. The wire type you choose will determine the
    exact driver you'll need. See the "interface" section of IC's at
    www.national.com or www.ti.com


    Well the 339 can do 30 volts output, OR 50 ohms, but not both at once.
     
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