Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

  • State
  • Locked Locked
  • Replies 11 replies
  • Subscribers 32 subscribers
  • Views 2255 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ULN2003 in our circuit

Barry OConnell
Prodigy 60 points
Other Parts Discussed in Thread: ULN2003A

We use and have used the ULN2003A in 1,000's of our products. As shown in the below circuit, our customer states that-The collector-emitter diode is a parasitic structure and should not be used to conduct current.

Is there any value/truth to that statement as to how we are using it? This is a 28 VDC device.; The "Coil" is 88 Ohms. So we draw approximately 320 mils to ground.

Thank You,

Barry

  • 0
    TI__Intellectual 1190 points

    Hello Barry,

    There is an internal "flyback diode" from Collector to COM pin essentially doing the same thing as your external diode D2. Why not use those?

    The collector to emmitter diode is parasitic and will conduct if collector-emmiter junction is reverse biased. I don't see that happening based on this schematic though.

    Thanks

  • 0 in reply to Andrew Leverette
    Prodigy 60 points

    So this is Okay as far as you can see for driving a solenoid coil?

  • 0 in reply to Barry OConnell
    TI__Intellectual 1190 points

    Barry,

    I can not see the image. Were you trying to attach one?

  • 0 in reply to Andrew Leverette
    Prodigy 60 points

    Andrew,

    Did you see the schematic in the first email I sent?

  • 0 in reply to Barry OConnell
    TI__Intellectual 1190 points

    Ok. So you were refering to that schematic.

    No. I do not see any issues with that implementation.

  • 0 in reply to Andrew Leverette
    Prodigy 60 points

    Okay, so the reason we are asking questions about this chip is because we received back one of our products (Called a "Switch") from a cusotmer and the 88 Ohm Coil was overheated and burned to the point that the coil measured 18 Ohms due to burned insulation of the magnet wire. We also found that the ULN2003A was blown. There is a fracture in the case from over stress. Our cusotmer is blaming our switch. We do not supply Voltage or Logic to the switch. The customers Power Supply and Driver does.

    And so we have more questions-

    1. Can a transient voltage of 3mS or less damage both the Logic and current side of the IC?(same question with concern that the spike went negative as well as high voltage)
    2. At what voltage level could this occur?
    3. Can a transient voltage on the Logic side of the switch >7 volts damage both sides of the IC?
    4. If the inductive load on the IC had a short or near short and went into over current condition(we tie 3 legs together, so > 1.5 amps), could this damage both sides of the IC, and could it cause damage to the System Driver on the Logic side?

      

  • 0 in reply to Barry OConnell
    TI__Intellectual 1190 points

    What is the ambient temperature?

  • 0 in reply to Andrew Leverette
    Prodigy 60 points

    Just got the temp +55 degrees C.

    Thank You.

     

    Barry

  • 0 in reply to Barry OConnell
    TI__Intellectual 1190 points

    Barry,

    At ~1.5A you are putting >2W on the chip causing the junction to rise to >200W (considering that was a SOIC in the above pic). This is enough for the chip to blow up.

    Seeing that these are current controlled devices(BJTs) and Beta decreases with collector current, the base could be sinkink much more current than the driver can allow in order to drive ~500mA/ch.

    Or the part just overheated and the base/login_input got shorted to ground and the driver was over driven causing damage.

  • 0 in reply to Andrew Leverette
    Prodigy 60 points

    We are only pulling 320 mA thru to ground. Not sure where you see 1.5 A.? We are surmizing the coil saw an over-voltage (not sure of what or how long) the coil began to burn, resistance went down, current went up> Chip blew. With the 3 legs tied together as we show on the schematic, what is the real current max that can handle?

    We also sent these questions previously-

    1. Can a transient voltage of 3mS or less damage both the Logic and current side of the IC?(same question with concern that the spike went negative as well as high voltage)
    2. At what voltage level could this occur?
    3. Can a transient voltage on the Logic side of the switch >7 volts damage both sides of the IC?
    4. If the inductive load on the IC had a short or near short and went into over current condition(we tie 3 legs together, so > 1.5 amps), could this damage both sides of the IC, and could it cause damage to the System Driver on the Logic side?

    Thank You

     

  • 0 in reply to Barry OConnell
    TI__Intellectual 1190 points

    1. Yes, Depends on the amount of Voltage.

    2. Anything <100V shouldn't cause any damage at that rate.

    3. No

    4. Yes. I answered that in the previous thread. That is where I got 1.5A from.