Help with 0.5v refrence voltage

Discussion in 'General Electronics Chat' started by STEVE PILCHER, Apr 6, 2013.

  1. STEVE PILCHER

    Thread Starter New Member

    Apr 6, 2013
    3
    0
    Hi all, please help with a project im working on.

    I need to generate a stable 0.5v refrence voltage.

    must be accurate within 0.05v and stable regadless of load.

    Any ideas?

    many thanks
    Steve
     
  2. #12

    Expert

    Nov 30, 2010
    16,278
    6,790
    Do you mean regardless of a million amps of load?
    I don't think anybody can do that.
     
  3. STEVE PILCHER

    Thread Starter New Member

    Apr 6, 2013
    3
    0
    let me clarify.

    Not regardless of load however load is unkown at this time, it will not exceed 1 amp

    Have had a little play with a voltage regulator today, but i doens't seem to like to drop below 1.5v and gets hotter the lower voltage it generates.

    this is the chip i've used http://cds.linear.com/docs/en/datasheet/3080fc.pdf and i have used the circuit in the data sheet with a variable resistor on the set pin.

    strangly however i have discovered that with a small fairy light bulb across the output it will adjust down to the desired voltage and stay cool, i cant recreate this effect with resistors though.
     
    Last edited: Apr 6, 2013
  4. #12

    Expert

    Nov 30, 2010
    16,278
    6,790
    Page 4 of the datasheet, 1 ma minimum load. It won't go to zero volts if it can't get rid of at least 1 ma. If you want to get to .50 volts, put a resistor on the output to waste 1 ma. 470 ohms will do the trick.

    Then you will have to adjust the Rset resistor to about 50,000 ohms. Use a 47k resistor and a 5k or 10k potentiometer to adjust it just right.
     
  5. STEVE PILCHER

    Thread Starter New Member

    Apr 6, 2013
    3
    0
    brilliant, thanks fo the help, must have overlooked that! should i run the resistor across the ouput on inline on the positive?
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    All linear regulators dissipate power as heat as determined by the voltage drop across them times the current through them. So naturally they get hotter as you lower the output voltage for a given current. For 1A output you will likely need to put it on a heat sink.
     
  7. #12

    Expert

    Nov 30, 2010
    16,278
    6,790
    No, you run it across the output on inline on the ground of your circuit.
     
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