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ULN2003A: What is sustain voltage of ULN2003A?

Kazuya Nakai59
Guru 22295 points

Part Number: ULN2003A
Other Parts Discussed in Thread: ULN2004A

Tool/software:

Hello guys,

One of my customers is considering using ULN2003A instead of ST ULN2064B.

ULN2064B
https://www.st.com/content/ccc/resource/technical/document/datasheet/07/e7/0f/b6/ef/2d/41/88/CD00000177.pdf/files/CD00000177.pdf/jcr:content/translations/en.CD00000177.pdf

At this moment, they have the following questions.
Could you please give me your reply?

Q1.
ULN2064B datasheet says "Sustaining voltage at least 35 V" on page 1 of the device datasheet.
What does the sustaining voltage means?

Q2.
Which parameter in the ULN2003A datasheet does this sustain voltage correspond to?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    TI__Mastermind 35010 points

    Hi Kazuya.-san,

    Q1. From the Electrical Characteristics table on page 6, I believe that this refers to the VCE required to sustain 100mA when the input is 0.4V.

    Q2. This parameter can be derived from VCE(sat) and VI(on).

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Guru 22295 points

    Hi Patrick,

    Thank you very much for your reply.

    I think the sustaining voltage is not VCE(sat) because ULN2064B datasheet says "Sustaining voltage at least 35 V"

    Is the sustaining parameter not described in the ULN2003 datasheet?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 35010 points

    Hi Kazuya.-san,

    Traditionally, the sustaining voltage is the collector-emitter breakdown voltage when the base is floating.

    This data sheet seems to refer to the sustaining voltage as the voltage at which Ic = 100mA when Vi = 0.4V. So when Vi = 0.4V and Vc <= 35V, Ic will be <100mA.

    ULN2003A sustaining voltage is much higher, which can be seen by the ICEx being <500uA when Vc = 50V and Vi = 1V.

    So, when the input is partially high but below the input ON threshold, ULN2003A will conduct (much) less than ULN2064B, and thus ULN2003A behaves much more like an ideal switch.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Guru 22295 points

    Hi Patrick,

    Thank you very much for your reply and I'm sorry to be late my response.

    Could I ask you an question about ULN2003A ICEX?
    I think that ICEX spec at VI=1V condition of ULN2003A is not described in the device datasheet.
    Is ULN2003A ICEX spec at VI=1V same as ULN2004A one (500uA)?

    Your reply would be much appreciated.

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 35010 points

    Hi Kazuya.-san,

    That's a good point, thanks.

    I think we can look at the I(off) spec instead, since Icex at Vi = 1V may not be the same for ULN2003 and ULN2004.

    Based on the below image and the functional block diagram, we can calculate Vi = 645mV min. So thus, at Vi = 645mV, Ta = 70C, and Vce = 50V, Ic will be 500uA max.

    I think this is a fair comparison to the sustaining voltage specification.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Guru 22295 points

    Hi Patrick,

    Thank you very much for your strong supports.

    Could you please tell me how you calculated Vi, 645mV?
    645mV=(2.7kohm+7.2kohm+3kohm) * ((Vbe(sat,min) of 1'st transistor from input B in Figure 7-2)/7.2kohm)?

    Could you give me your reply?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    Guru 22295 points

    Hi Patrick,

    Could you please give me your reply?

    Thank you and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 35010 points

    Hi Kazuya.-san,

    645mV was calculated using: 50uA * (3k + 7.2k + 2.7k), since neither VBE will be high enough to turn either transistor on.

    Thanks,

    Patrick