LM3886 In parallel - overheating issues

Discussion in 'The Projects Forum' started by Alicec63, Aug 2, 2013.

  1. Alicec63

    Thread Starter New Member

    Jun 20, 2013
    12
    0
    Hi,

    I am currently using the LM3886 in a parallel setup as explained in app note. AN-1192.

    I am using it to drive the DC supply of a Radio - which draws approx 6A at 12V, so essentially a 2ohm load.

    I was previously using the LM4766 in a bridged setup, but this was for a radio drawing 1A at 12V - which worked perfectly.

    Due to the increased power I looked at using the LM3886 in parallel as this looked like it could provide enough power easily.

    When testing on a test load, set at 100 ohms, the parallel setup worked fine. As soon as I dropped the resistance to 12Ohms, the output of the amplifier became unstable. I think this is due to the IC's getting too hot?
    The IC's are heatsinked and have a fan on them - so this shouldnt be the case? Maybe this is due to some sort of inbalance between the 2 IC's? They are both set with a gain of 2 - 0.1% resistors, and have an output series resistor with a value of 0.1Ohms. Power supply is +/-24V.

    When driven individually, they work fine, its only when in a parallel setup I am seeing the problems.

    Any ideas on what is going wrong?

    Thanks
     
  2. Ramussons

    Active Member

    May 3, 2013
    557
    92
    Circuit schematic ?

    Ramesh
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    As Rasmussons said, we need a schematic.
    LM3886 is intended to be used as an audio amplifier. Why are you trying to use it as a power supply regulator?
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Makes no sense to try to use a audio amp as a DC voltage regulator.

    You could easily build a 6A linear reg with the LP2975:

    http://www.ti.com/product/lp2975
     
    Last edited: Aug 2, 2013
  5. gootee

    Senior Member

    Apr 24, 2007
    447
    50
    The LM3886 is designed to be stable at closed-loop gains of 10 or greater.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Has Alice gone back to Wonderland?
     
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