Question about the LD1086-50 voltage regulator

Discussion in 'General Electronics Chat' started by sstbrg, Dec 31, 2009.

  1. sstbrg

    Thread Starter Active Member

    Nov 29, 2008
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    I'm using a D2PAK LD1086-50 (5v regulator) on my printed circuit board.
    I'm connecting it to a 15V supply (a GAIA converter) and, quite obviously, it generates lots of heat and sometimes shuts itself down.
    The only peripherals I added are a couple of capacitors, like in the datasheet's typ. application circuit.

    Anyway, main question is how to reduce the heat with minimal peripheral additions (I want to keep the prototype board very clean from various glues and wires :D). Maybe a simple heatsink will do the job?
    Also, as far as I understood the 1086 has an adjustable version, so can I use two resistors to get 5V from the adjustable version of this regulator (LD1086V) without generating a lot of heat?

    Is there a better regulator sold in the same package with the same pin configuration?

    If you feel like giving any additional advise, please do :)

    DS: http://tick-tock.googlecode.com/files/LD1086V33.pdf
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If it's getting hot with just capacitors attached, you have a problem. Perhaps your caps are shorted internally, or you connected the regulator incorrectly.

    At any rate, with an input of 15v and an output of 5v, over 2/3 of the power will be dissipated in your regulator as heat. There's really no getting around that when you're using a linear regulator.

    A low dropout regulator doesn't do you any good if you're supplying it with a high voltage - it'll still dissipate a lot of heat.
     
  3. sstbrg

    Thread Starter Active Member

    Nov 29, 2008
    54
    0
    Thanks for the quick reply! :)

    Do you see any good way to at least reduce the level of heat?
    Perhaps even gluing an additional regulator somehow in-between?
    Maybe using a different regulator?
     
  4. VoodooMojo

    Active Member

    Nov 28, 2009
    503
    53
    a possible aid would be to cascade a 12 or better yet 9 volt regulator in line with the 5 volt.
    this would shunt a good portion of the heat away from the 5 volt regulator, and more evenly distribute it across your board.


    be aware that the first regulator will carry both the current through itself and the current being used by the second regulator.

    use an appropriate heat sink for the current/heat generated.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Giving your regulator an input voltage of 6v to 7v would eliminate most of the heating.

    One way to do that would be to use a switching regulator between your 15v supply and your LDO regulator. This could be very efficient, but will generate a lot of electrical noise if not designed and built carefully.

    A "brute force" method would be to simply use a series of fixed resistors or one heavy-duty rheostat between your 15v supply and your LDO regulator input. This can easily cause your voltage regulation to be very poor if the load is dynamic, or the regulator to shut down if the correct resistance is not selected.
     
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