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Voltage Regulator +Negative Voltage Generator

Discussion in 'General Electronics Discussion' started by jpanhalt, Feb 15, 2014.

  1. jpanhalt

    jpanhalt

    426
    4
    Nov 12, 2013
    I started a project that needs -5V for a GLCD display and +5 volts for everything else. Actually, if it weren't for the display, I could use +3.3V for everything else.

    At the outset, I used a MAX851 for the negative supply. It was in my box of parts, and unlike the ICL7660, it has a shut down pin. The +5V was from a bench power supply.

    I am going from breadboard and bench power supply to a prototype with batteries. Lithium batteries are desirable, but NiMH is OK.

    Can anyone suggest a voltage regulator/converter that produces -5V and +5V simultaneously from a single supply of lower voltage? The -5V doesn't need to be regulated. The +5V should be regulated as it drives a PIC and the display. Maximum current for the -5V is low, but undetermined. Maximum for the +5V is ≤100mA.

    I have looked at the ST0D03B (http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00044917.pdf) which seems like it offers most of what I need. But, one cannot enable V+ and V- separately (the GLCD datasheet cautions against having V- without V+), the +5V is not regulated, and it has the DFN package. I prefer something like an SOIC for hobby work. I find DFN's hard to remove, but that is not a show stopper by itself.

    Does anyone here have experience with that chip or other chips of similar function that you can recommend?

    John
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,077
    Dec 18, 2013
    Been looking for something like that myself John. I Can find one either, I asked Linear Tech and they said no never been asked for that before??? Let me know if you find something. I'll have another dig about also.
    Adam
     
  3. jpanhalt

    jpanhalt

    426
    4
    Nov 12, 2013
    To keep it simple, I just went with a couple of separate IC's I had laying around. The Max851 (obsolete) for -5V and a Sharp PQ1L for +5V. If I need a negative bias voltage for a future project, it can be generated with a PWM output from the controller.

    John
     
    Last edited: Feb 17, 2014
  4. Arouse1973

    Arouse1973 Adam

    5,164
    1,077
    Dec 18, 2013
    Ok Cool
     
  5. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi,

    If you have a MAX232 (or3232) on the board you can have neg bias supply for free or you can use one just for that purpose.

    Olivier
     
  6. Arouse1973

    Arouse1973 Adam

    5,164
    1,077
    Dec 18, 2013
    That's an interesting suggestion, never done that before. What is the max current output and what would the load regulation be like?

    Adam
     
  7. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Maximum current will be around 10mA. The output is a bit lower than twice the supply voltage they are no load regulation but it's fit the needs for a LCD neg bias. I have used such config with 2 of the MAX3232 drivers for a debug port and a large 4X20 LCD.

    Olivier
     
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