LT3080 regulator question

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

  1. buzaiandras

    Thread Starter Member

    Jul 18, 2011
    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,

  2. JDT

    Well-Known Member

    Feb 12, 2009
    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
    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
    @JDT Thank you. I'll try that. :)