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Logic Level Compatibility

  1. Sep 6, 2006 #1
    I'm working on a project that uses an ATMEGA32L uC (3.3V supply) and requires a couple high current outputs. To accomodate the requirement of the outputs I'd like to use a ULN2003A darlington transistor array but my concern is that the logic levels of the ATMEGA32L and ULN2003A aren't completely compatible (VOH in particular). Since I'm just a beginner, would somebody mind commenting on the compatibility between the outputs of the ATMEGA32L (3.3V supply) and the inputs of the ULN2003A?

    http://www.atmel.com/dyn/resources/prod_documents/doc2503.pdf" [Broken]

    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Sep 6, 2006 #2


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    The 2003 I believe has a 2.2K series resistor on each input. I didn't look at the data sheet, I'm going off of memory. It is most certainly made to work off of 0 or 5 volt logic levels. However, depending on what you have hanging on the output of the 2003, the 3.3 volt input may work just fine. The thing that could be a problem is the output transistor may not be turned on all the way and dissipate more power than it normally would due to the voltage drop across it. It really depends on your specific application.
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