Logic datasheets?

Discussion in 'General Electronics Chat' started by Coollestersmooth, Dec 28, 2014.

  1. Coollestersmooth

    Thread Starter Member

    Dec 18, 2014
    72
    0
    trying to decipher some logic datasheets and am curious,
    recommended operating conditions are pretty obvious however i am wondering what is meant by "electrical characteristics over recommended operating free-air temperature range"
    i would assume that the values stated are measured input/output values for that IC at various operating temperatures, however on a lot of datasheets some of the values stated are wildly different from those of the recommended operating conditions for example:

    http://www.ti.com/lit/ds/symlink/cd54ac08.pdf

    here IOL/IOH = +/-24mA in the recommended operating conditions,
    yet when looking at the free air operating charistics chart under VOH at a Vcc of 1.5V-4.5V IOH = 5o micro amps, a few boxes bellow that at Vcc=4.5A IOH= 24mA
    am i to understand that IOH can be set? is this just variation with load resistance or am i just misunderstanding what is meant by "electrical characteristics over recommended operating free-air temperature range".
     
  2. Coollestersmooth

    Thread Starter Member

    Dec 18, 2014
    72
    0
    i have found the answer, current at the output for testing is forced in order to minimise power dissipation, its in the smaller notes at the bottom, the devil is in the details......
     
  3. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    Without trying to address the specific example you mentioned, most of the specs give min, typical, and max values (or some subset of them). When operating at the recommended temperature, there is a range between min and max. Not surprisingly, if you consider a broad temperature range there will probably be some temperature at which the value is smaller than the min at the recommended temperature and probably a different temperature at which the value is larger than the max at the recommended temperature, so the broader the temperature range the broader the range of values you need to allow for. Note that few data sheets give 'typical' values over a large temperature range, but only min and max.
     
  4. Coollestersmooth

    Thread Starter Member

    Dec 18, 2014
    72
    0
    thanks, this is as i assumed, i was just thrown by the multiple values for IOH at a single supply voltage.
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    You might want to have a look at the attached PDF.

    Bertus
     
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