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ULN2803A: Can I use an adapter to provide 48V to the loads connecting the ULN2803A

Xiang Maverick
Intellectual 750 points

Part Number: ULN2803A

My ULN2803A connects a resistive load and an inductive load with differenent channel. The two loads are powered by the same 48V voltage source, which is provided by an adapter. The COM pin is also connected to the 48V power. I do not place any capacitance to the 48V voltage source. The upper limit of VCE of ULN2803A is 50V, which is only 2V larger than 48V power. Will it be too dangerous to do so considering the switches of the resistive load and the ripple and inaccuracy of the adapter? Should I add capacitance to the 48V voltage source?

  • 0
    TI__Genius 13460 points

    Hello,

    Thank you for reaching out to the E2E forum!

    The ULN2803 should be able to drive your loads, but from a design stand point I believe you're giving yourself to small of a margin for the voltage ripples. An input capacitance can mitigate this ripple in the voltage but could potentially harm the device if the event of an over voltage. A similar device to the ULN2803A with a 100V rating is the SN7546. I would recommend taking a look into this device and see if it meets the rest of your needs. The 100V rating of the SN7546 will assure you won't damage the device.

    Let me know if you have any questions regarding these devices.

    Regards,

    Andy Robles

  • 0 in reply to Andy Robles
    Intellectual 750 points

    Why An input capacitance could potentially harm the device if the event of an over voltage? If no input capacitance exist, will over voltage harm the device. If I decrease the power to 24V, given the VCE upper limit is 50V, is the input capacitane needed?

  • 0 in reply to Xiang Maverick
    TI__Genius 13460 points

    Hello,

    I apologize for the confusion. I meant that the capacitor could help reduce the voltage ripples, but even with a capacitor the device could still be harmed if you work with 48V on a device with a max of 50V. The capacitor can only reduce the voltage ripples so much, and giving yourself a 2V cushion might not be enough.

    Is is still possible to reduce your voltage to 24V? With these conditions the device should not have any problems.

    Regards,

    Andy Robles

  • 0 in reply to Andy Robles
    Intellectual 750 points

    If I use 24V power, is the use of a capacitor recommended

  • 0 in reply to Xiang Maverick
    TI__Genius 13460 points

    Hello,

    I do recommend the use of input capacitor for a more robust system. These capacitors help reduce the voltage ripples, supply current during transients which help with stability, and other anomalies that sometimes may be present in a system.

    Regards,

    Andy Robles