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Linear power supply regulator 5V 2A with 7805

ABED Amor
Prodigy 20 points

I need to create a +5V 2A supply from a single floating 12 V source.  Can I do that with the LM 7805 for the +5V

Thanks for your help.

  • 0
    Guru 22270 points

    Hello ABED,

    With a large heatsink and a fan you might be able to get away with it.  The CT versions are generally rated for a bit more than 1 amp.

    Check the data sheet for the LM78xx family. It should have example circuits that allow you to boost the current output using an external transistor.

    Thanks,

  • 0
    TI__Guru**** 165326 points

    Abed,

    It is possible to add a transistor to boost the LM7805 output current.
    The total power dissipation will be (12V-5V)*2A = 14 watts.

    However, I suggest using "Webench Designer" on the main http://www.ti.com/ web page.
    Enter 12V for VIN min and max. Enter 5V for output and click red "start design" button.
     

  • 0
    Prodigy 20 points

    hello  greenja,

    thanks for your help, I do the schematic for Figure 14 ( High Current Voltage Regulator) in the datasheet and i change the BD536 transistor with the BD676, but the this is heated

  • 0 in reply to ABED Amor
    Guru 22270 points

    Hello ABED,

    The data sheet I have for that device uses a MJ2955 in Figure 9.  the BD676 should be adequate for a 2 A load.

    Just what is getting heated?  Are you using heatsinks?  How close are the two components to each other on your board?

    Thanks,

  • 0 in reply to ABED Amor
    TI__Mastermind 22610 points

    You need to dissipate 14Watts, so yes, this is inefficient and it is going to get hot. The point of adding the parallel transitor is to reduce the power dissipation in the LM7805 down to an acceptable value which requires having the transitor be hotter than the LM7805, perhaps much hotter depending on your package choice for LM7805.