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Original question:

ULN2803A: output current curve under different duty cycle of control signal.

ULN2003A: Small package, 3 channels output and 50% duty cycle to support total 750mA output

Yue TANG
Expert 8695 points
Part Number: ULN2003A

Hi,

My customer use ULN2003A to drive 7 electronic valve.  they need 3 channels output  simultaneously to support 750mA under 50% duty cycle, other channels 

but according to the curve below, the peak current of each channel  in this condition can only output more than 200mA current, very close to 750mA margin. 

they prefer small package, would you please suggest if this is  feasible? or recommend other device. thanks.

 

  • 0
    TI__Genius 13760 points

    Hi Yue,

    Thank you for reaching out to the E2E forum!

    I would like to ask some questions regarding the following problem to ensure my understanding:

    1. Will you be using 3 channels of the ULN2003 to drive all 7 electronics valves or you will use 7 ULN2003, one for each valve? Meaning each UN2003 will only be using 3 channels and the rest of the channels will not be connected.

    2. What is your operating voltage? (To see if we have another device that could suit your application)

    Regards,

    Andy Robles

  • 0 in reply to Andy Robles
    TI__Expert 8695 points

    Andy,

               1. They used 1 UL2003 to drive 7 valves, 3 channel open at the same time could happen.

                 2. Will check with them tomorrow

  • 0 in reply to Yue TANG
    TI__Expert 8695 points

    their working voltage is 12V. 

  • 0 in reply to Yue TANG
    TI__Genius 13760 points

    Hi Yue,

    Is there a reason why they don't want to use 4 channels from the ULN2003A to drive these electronic valves?

    Using 4 channels you limit each channel to conduct up to 200mA. If output are connected together you could achieve up to 800mA.

    Regards,

    Andy Robles

  • 0 in reply to Andy Robles
    TI__Expert 8695 points

    Andy,

    Actually, they need to use 3pcs ULN2003A to drive up to 17 valves. I'm checking why they use duty cycle to limit output.   please suggest if I reduce the duty cycle, each channel will output more current, right? I mean 3 channels conduct at the same time scenario.  as below picture show, if duty cycle is 40%, the output current  will increase up to 400mA, N=3. 

  • 0 in reply to Yue TANG
    TI__Genius 13760 points

    Hi Yue,

    That is correct. The lower the duty cycle the higher the current you'll be able to drive. But this means that you will only be able to use 3 channels at a time to achieve the desired current.

    Do keep in mind that in the datasheet there are 2 of these curves, one for the N package and one for the D package. Ensure you are using the correct one for the design.

    Regards,

    Andy Robles