Level converter with wide input tolerance

Discussion in 'The Projects Forum' started by nfogh, Nov 2, 2012.

  1. nfogh

    Thread Starter New Member

    Nov 2, 2012

    I am trying to get a hold of (or build) a level converter with a very wide input range. Basically, I want it to translate any voltage over 1 V to 3.3V, and any voltage below 1V to 0V. It should be able to accept a large input voltage range. At least -20V to 20V. I have tried to search for a solution in an IC, but they don't have the input range I am looking for. I was considering building a CMOS inverter using a chip with complementary PMOS and NMOS devices, as that is the only devices that will accept such a large input voltage range. I am not sure that is the best way to do it, though. Does anyone have some input, or an idea for another solution?

    Best regards,
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
  3. nfogh

    Thread Starter New Member

    Nov 2, 2012
    I forgot to include, that I only have ground and 3.3V in my circuit. The input signal will be coming from outside my circuit.
  4. John P

    AAC Fanatic!

    Oct 14, 2008
    If you aren't too fussy about the changeover point, all you need is a CMOS input and a resistor. The chip will have protection diodes that protect the input from damage, provided that the current is kept small.
  5. crutschow


    Mar 14, 2008
    If you want a reasonable accurate trip point then use a comparator, such as an LM339 with the minus input biased to +1V and a resistor on the output tied to 3.3V. You also want to add a small amount of hysteresis so it doesn't oscillate at the trip point (see the LM339 data sheet for detail on the non-inverting comparator circuit.

    To protect the input you could use diodes after the resistor at the plus input. Connect a Schottky diode with anode to ground (to clamp negative voltages) and two regular diodes (so the clamp voltage is above 1V) in series with cathode to ground (to clamp positive voltages).