Power Supply Balancing

Discussion in 'General Electronics Chat' started by chrisw1990, Jan 26, 2012.

  1. chrisw1990

    Thread Starter Active Member

    Oct 22, 2011
    Ok, probably a simple fix, not sure how to do it..
    i have two power supplies on my project, both outputting 3V3, but one is designated to the uP and EEPROM and other Memory. the other is a 4A for screen and additional peripherals.
    my question is a 2part i guess, some consideration leads me to believe i need to balance the power supplies, as theres analogue conversions, so if one is a few millivolts off, it wont be as accurate..
    therefore, based on this, do i need to put a resistor or diode in linking the two power supplies? obviously the uP supply cannot backpower the additional peripherals, however the forward voltage drop of a diode would mean it wouldnt actually balance the supplies?
    my question...
    a) Do i need to balance the supplies?
    b) If so, how do i go about it?
  2. crutschow


    Mar 14, 2008
    a) No. If your design needs balanced supplies then it is not a good design. For analog conversions you do not use the power supply as a reference. Use a separate accurate voltage reference IC for that purpose. You can use one reference for all the conversion requirements so they will not be affected by the supply voltages. The value of the supply voltage to a converter does not affect its accuracy, only the value of the reference voltage (which is sometimes internally generated from the supply voltage).
  3. Wendy


    Mar 24, 2008
    The term is dual tracking, as in one power supply tracks the other.

    Most circuits don't care, though there are a few that do.

    A direct equivalent is Creating a Virtual Power Supply Ground.

    You can use one power supply with something like this.

    There are huge numbers of ways to create a fixed voltage reference inside a circuit, 3 terminal regulators probably being the easiest, along with zener diodes.
  4. crutschow


    Mar 14, 2008
    If he needs a few millivolts of accuracy, a 3 terminal regulator or most zener diodes are not stable enough with temperature. He would need a voltage reference IC.