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ULN2003A: maximum collector current figure 4

Toshihiro Watanabe
Genius 10235 points
Part Number: ULN2003A

Hello,

There are some post relating this topic but I am still not sure our usage is possible. Please let me ask this.

1. What is made limit?

Figure 4, D package duty vs current graph

 This limit will come from power dissipation. Do I think correctly?

2. Duty estimation

 We use 6 of 7 channels. 6 channels split by 2 group, group 1 and group 2. Each group has 3 channels. Each group requires the same current like 100mA each.

 There are four status. 

  1) Group 1 current flow, Group 2 doesn't flow  -> called this 1

   2) Group 1 current flow, Group 2 flow               -> called this 2 (= 1+1)

   3) Group 1 doesn't flow, Group 2 flow               -> called this 1

   4) Group 1 doesn't flow, Group 2 doesn't flow  -> called this 0

1,1,2,1,1,0,0,0 is repeated. I assumed this duty cycle 75% (= 6 / 8). Is this estimation right?

3. Total drive ability

Assumed this 75% duty, I can see each channel can flow around 95mA from figure 4. We combine 3 channels so total around 285mA load can drive.

Is my estimation correct?

I think ULN2003A can drive around 285mA load when ambient temperature is 70C. Would you review if I can consider correctly?

Best regards,

Toshihiro Watanabe

  • 0
    TI__Genius 10235 points
    Hello,
    Please let me know the right estimation way if my idea is incorrect.
    Best regards,
    Toshihiro Watanabe
  • 0 in reply to Toshihiro Watanabe
    TI__Genius 10855 points

    Hi Watanabe-san,

    Thanks for providing me with the detailed application. Please find the answers to your questions below:

    1. What is made limit?

    [AH]: Correct, the maximum currents are limited by the self-heating of the device. As long as the device remains within the thermal junction range, you can operate with the current rating.

    3. Total drive ability

    [AH]: I don't see any issues with the estimation, since you are assuming "worst-case" scenario. The maximum current you estimated is a good measurement for the device.

    Thanks,

    Arthur Huang

    To find the latest information on Power Switches, visit www.ti.com/powerswitch

    Please click "This resolved my issue" button if this post answers your question.