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delser9
Visitor II
July 23, 2004
Question

ST7FLITE29, I/O current maximum

  • July 23, 2004
  • 8 replies
  • 1256 views
Posted on July 23, 2004 at 07:40

ST7FLITE29, I/O current maximum

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    8 replies

    D
    delser9Author
    Visitor II
    July 21, 2004
    Posted on July 21, 2004 at 06:08

    Dear all,

    can anybody tell me what is the maximum current that may permanently be sourced by a standard I/O pin, on a ST7FLITE29.

    In the datasheet I could not find any limits other than the 'Absolute maximum ratings' which are not given for 'extended periods', but only for short time stress. But I'm looking for long time, permanent current ratings.

    The currents mentioned on p106 are never higher than 5mA for standard I/O, but it does not say that it is limited to 5mA.

    The total current into Vdd power lines is only 10mA, without the I/O mentioned above. Therefore there is nor problem with total current.

    Thank you for any hints where I may find that information on the datasheet.

    Best Regards,

    Alfredo
    L
    ldefend2
    Visitor II
    July 21, 2004
    Posted on July 21, 2004 at 12:20

    You are right, current mentioned is never higher than 5mA for standard I/O and the range between 5 to 25mA (ABSOLUTE MAXIMUM RATINGS) is not warranted. Concerning in my opinion 5mA is a decorous value for a standard pin.[addsig]

    D
    delser9Author
    Visitor II
    July 21, 2004
    Posted on July 21, 2004 at 13:41

    Hello Luca

    could you please tell me what you mean with 'decorous value'?

    I am wondering whether it is a problem to drive 7mA permanently with a standard pin or not.

    Maybe there is somebody from ST out there caring about customers questions?

    Thanks for your help.

    Regards

    Al

    A
    anshul
    Visitor II
    July 22, 2004
    Posted on July 22, 2004 at 02:35

    Hello Al

    Yes, you can drive 7 mA permanently by a standard I/O but your Voh value would decrease.

    But an important point is that the total I/O current sourced must be within the maximum rating specified for the particular device.

    Regards

    Ansh

    D
    delser9Author
    Visitor II
    July 22, 2004
    Posted on July 22, 2004 at 04:53

    Hello Ansh

    thanks for your kind help.

    Could you please tell me how you got that information? Is that an official statement from ST? Where can I find it in the official documents of ST? Maybe any documents I did not see on the ST website?

    Regards

    Al
    A
    anshul
    Visitor II
    July 22, 2004
    Posted on July 22, 2004 at 10:02

    Hello Al,

    I am referring to the ST72F324 datasheet for eg. from the following link

    http://www.stmcu.com/files/mcu/1086775516.pdf

    Here on page 117, you have the absolute maximum ratings under the current characteristics section.

    Then on page 35, you have a graph which shows the Voh (typical) vs Iio graph.

    This kind of data would be available on each datasheet, so depending on the MCU you are using you can refer the corresponding datasheet.

    Best Regards

    Ansh
    D
    delser9Author
    Visitor II
    July 22, 2004
    Posted on July 22, 2004 at 11:53

    Hi again,

    you are right that data is in the ST7FLITE29 datasheet indeed. But the Iio graph ends at 5mA. That is the reason why I doubt whether it is possible to drive 7mA permanently.

    Greetings,

    Al
    A
    anshul
    Visitor II
    July 23, 2004
    Posted on July 23, 2004 at 07:40

    Hello Al,

    I agree the graph in the Lite2 datasheet does not show 7mA. But in table 13.3.2 it is mentioned that the maximum output current sources by any I/O or control pin is -25mA.

    Best Regards

    Ansh
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