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ULN2003A Driver

  1. Aug 4, 2007 #1
    I recently purchased a few ULN2003A chips with the goal of eventually powering a stepper motor. So far I'm just testing out the chips, but I've run into a bit of a roadblock. I'm not quite sure how to use the chips.

    My setup is as follows:
    I have connected pin 8 (gnd) to gnd. I have supplied pin 1 (in 1) with 5 VCC.
    Using a resistor (because I don't have any LEDs) I have supplied one lead with 5VCC and the other lead to pin 16 (out 1). I then proceed to measure the voltage drop across the resistor and I get about 5 volts.

    Since I'm supplying a constant voltage to pin 1, shouldn't it be stepped up to ~50V (the maximum)? Is my understanding of the chip's operation incorrect? Or do I just have the setup wrong?

    The datasheet is available here [link]http://www.ortodoxism.ro/datasheets/SGSThomsonMicroelectronics/mXtyyvx.pdf[/link]
    Last edited: Aug 4, 2007
  2. jcsd
  3. Aug 4, 2007 #2


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    The output voltage is limited to the supply voltage.
    You should get slightly less then 5v with a 5v supply.
  4. Aug 5, 2007 #3


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    The 2003 is simply a darlington transistor array with all of the emitters connected together to one pin of the IC which is usually grounded. This IC does NOT step up voltage if that is what you are after. I believe the collector of each transistor is tied to the high voltage lead through a diode which forms a flyback protection circuit to protect the transistors against inductive loads.
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