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ULN2803A: ULN2803A

Part Number: ULN2803A

If COm pin supply does not affect control inputs , Shall i connect 3.3v to COM pin and  operating control inputs with 3.3v TTL or CMOS?

  • Hi Gayathri,

    The COM pin is like a power pin for this device. I would recommend connecting it to the highest voltage rail possible with respect to the output. If the output voltages are 3.3V then the 3.3V rail is acceptable. It should be directly connected to this voltage rail as shown in the datasheet here:

    It is possible to use COM at higher voltages compared to the output but it is not acceptable to set COM to a lower voltage than the output since the internal diode will always be forward biased.

    Thanks,

    Shreyas

  • Thank you for your reply.outputs are open collector right? how much pullup resistance value to be connected to that?

  • Hi Gayathri,

    These are low side switches. The pull up resistance would be your load in this case. As such, your load will go between the power rail and the low side switch.

    Thanks,

    Shreyas