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0-5V adjustable voltage regulators?

Discussion in 'Electronic Design' started by [email protected], Jun 27, 2007.

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  1. Guest

    Anyone know of an adjustable voltage regulator that:
    -outputs 0-5V (or 1-5V)
    -can source 100mA over that range
    -is powered by 6V

    ?

    Thanks.

    KCJ
     
  2. D from BC

    D from BC Guest

    A low drop out type might be needed.
    ~1V to 5V adjustment more probable due to internal references
    typically around 1V to 1.5V.
    As an example:
    http://www.fairchildsemi.com/ds/FA/FAN1117A.pdf
    It's not great but all I can think of for now..
    D from BC
     
  3. ehsjr

    ehsjr Guest

    A dc-dc converter chip like the TI MC33063 and a few external
    components will do it, except the minimum is 1.25 volts.

    http://focus.ti.com/lit/ds/symlink/mc33063a.pdf

    Since your current requirement is low, you can use a
    trick to get down below 1 volt:

    Vin--[Regulator]Vout---+
    | |
    | [Load]
    | |
    | [D1]
    | |
    | [D2]
    | |
    Gnd ------+------------+

    or
    Vin--[Regulator]Vout---+
    | |
    | [Load]
    | |
    +------------+
    |
    [D1]
    |
    [D2]
    |
    Gnd ------+

    If you short out D1 and D2 when Vout needed
    is above 1.25, you get better regulation.

    Note that [Regulator] above is used to
    represent the complete regulator circuit
    and its associated components - the drawings
    are intended to show only the addition of the
    two diodes, not the complete circuit.

    Ed
     
  4. whit3rd

    whit3rd Guest

    Most 'adjustable regulators' use a resistor divider on the
    output and compare to a fixed (1.2V typically) reference, so
    they only go to 1.2V minimum. Three-terminal and four-terminal
    regulators are ruled out.

    The LM10 op amp includes a voltage reference, and can get close
    enough to the rails to do what you want, except the 100 mA
    part. Can you settle for 20 mA?

    Add a pass transistor to the LM10 and it's easy.
     
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