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Smallest way to get -5v

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  • Smallest way to get -5v

    What is the smallest (least number of support components) method I can use to get -5v? My PSU was finished a long time ago and has zero space inside, but I now need to use my serial port so I have to add -5v. Is there such a thing as a linear reg that can do this?
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    (=========-) 99% complete
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    AMD K6/2 500 @ 450mhz to keep heat and power usage down, 64Mb, slim CDrom drive, 64mb USB pendrive for MP3 transfer, 10Gb 2.5" drive for MP3, USB>RS232
    All jammed in external CDROM drive case.
    Kenwood KVC-1000r In-Dash LCD. x-10 MouseRemote. Destinator V2 Gps. DC-DC with onboard Shutdown controller.
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  • #2
    All linear regulators will require a negative supply to generate a negative voltage. If you've already got a -12v supply then you can simply use a LM7905 voltage regulator along with a couple of caps on the input and output. If you don't have a negative supply to start with then your best bet is a MAX774 switch mode chip click here for details.
    And you say people actually pay money for M$ Windows?
    www.mp3mini.co.uk (Does what it says on the URL) www.openclassic.co.uk (The new car, with zero rust!) www.rob-web.co.uk (My other site)
    Total re-design underway: on the whole progress is very slow as the car is taking up too much time :)

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    • #3
      Unless you have a strange MB, you need -12 for serial ports. -5 is hardly ever used for anything anymore.

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      • #4
        Yeah, its for serial port, and I dont have a -12v line cause I never needed before.

        Guess Ill have to bite the bullet and order prts to built the Maxim 774/775/776 supply.
        -------------------------------------------
        (=========-) 99% complete
        --------------------------------------------
        AMD K6/2 500 @ 450mhz to keep heat and power usage down, 64Mb, slim CDrom drive, 64mb USB pendrive for MP3 transfer, 10Gb 2.5" drive for MP3, USB>RS232
        All jammed in external CDROM drive case.
        Kenwood KVC-1000r In-Dash LCD. x-10 MouseRemote. Destinator V2 Gps. DC-DC with onboard Shutdown controller.
        ----------------------------------------------

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