Best way to create -5V rail from 12v supply

Discussion in 'General Electronics Chat' started by Duxthe1, Nov 11, 2008.

  1. Duxthe1

    Thread Starter New Member

    Sep 27, 2008
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    I'm looking for a good way to create a -5v supply from +12v without splitting the 12v with diodes. I need to keep the 12v gnd in tact. I've looked at rectifying the neg side of a square wave from a 555 timer but the current output is low. I need to drive the negative side of 2 op-amps in a unity gain configuration.

    Suggestions?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    What is your current requirement for the -5v supply?

    More to the point, why don't you post your schematic, and give some details about the inputs you're getting, and what outputs you require?
     
  3. bertus

    Administrator

    Apr 5, 2008
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  4. m.majid

    Active Member

    May 28, 2008
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    hi

    i recommend to try LMC7660,
    see also MC34063A

    :)
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The x7660 gives extremely limited current output, less than the rectified 555-output scheme.
    Bertus' first link shows a scheme capable of 2A @-5V.
    The MC34063A datasheet from Texas Instruments shows a -5v 1.5A supply in the applications portion. That schematic could be adapted to a 555 solution if the 555 were driving an external transistor that sourced current to an appropriately sized inductor.
     
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