LT3080 regulator question

Discussion in 'General Electronics Chat' started by buzaiandras, Sep 7, 2012.

  1. buzaiandras

    Thread Starter Member

    Jul 18, 2011
    54
    0
    Hi everybody,

    I have a question about the LT3080 voltage regulator.
    The datasheet of the LT3080 voltage regulator says that "For true zero voltage output operation, this 1mA load current must be returned to a negative supply voltage."

    What exactly does this mean? How can I return the minimum required load current to a negative supply voltage? In case I have a single supply and I generate a negative voltage using a charge pump how would I connect the minimum load to the negative voltage generated by the charge pump?

    What I mean is how should I make the connections between the 1mA load and the charge-pump?

    Thank you,

    Buzai
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    To enable the output voltage to adjust down to zero, you need to dump at least 1mA output current to a voltage BELOW zero (a negative voltage).

    For example if you have a charge pump that generates -5V connect a 4k7 between this and the output.

    I suspect that this is the supply current for the internal error amplifier.

    If you have not got a negative supply rail, it will still work but the output voltage will not go right down to zero.
     
  3. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    Look at it like a center tapped DC power supply, +15v COM -15v

    LM317's are like that too, except at a slightly higher current. There should be a circuit example out there somewhere.
     
    Last edited: Sep 7, 2012
  4. buzaiandras

    Thread Starter Member

    Jul 18, 2011
    54
    0
    @JDT Thank you. I'll try that. :)
     
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