Will this resistor burn up?

Discussion in 'General Electronics Chat' started by chipwitch, Mar 15, 2014.

  1. chipwitch

    Thread Starter Member

    Mar 29, 2013
    48
    4
    I found the attachment in TI's LM150 datasheet. If the resistor won't burn up, would someone be kind enough to explain why not?
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,015
    Why would you expect it to burn up if your load needs less than 2 watts?
     
  3. #12

    Expert

    Nov 30, 2010
    16,318
    6,818
    Yep. That will smoke.

    The current limiting resistor will always have 1.25 volts across it.
    1.25^2 / .4 = 4W
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    +1 It's gonna cook. Marketing must have done that one on a Friday afternoon.
     
  5. chipwitch

    Thread Starter Member

    Mar 29, 2013
    48
    4
    That's what I thought... except I did it the other way... 3A^2 x .4Ω = 3.6W! Looks like they're fudging more than the wattage!
     
  6. chipwitch

    Thread Starter Member

    Mar 29, 2013
    48
    4
    Ya know... it's hard enough to learn without component manufacturers feeding ya garbage!
     
  7. #12

    Expert

    Nov 30, 2010
    16,318
    6,818
    Don't whine too much. They are right a lot more than they are wrong, like 999 to 1.
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    maybe, but that's because most of the data sheets had to go across my desk for final check before they got published.:p

    The LM317 was done before I worked there.
     
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