I made a +-2.5 Dual supply. Although, grounds are different. There is an issue!

Discussion in 'The Projects Forum' started by demerda2, Jan 21, 2016.

  1. demerda2

    Thread Starter New Member

    Jan 21, 2016
    So, I have this ADS that I am interfacing with a microcontrollter called C2000.
    ADS works with a dual supply (+2.5 and -2.5), and C2000 with a 5V.

    I made the following schematics and I can get a +-2.5V to supply the ADS1299.

    I use the C2000 to interface with ADS1299, which means that both grounds should be tied together.

    The whole system consumes around 50mA.

    And according to this schematic that i made, this isn't possible because the references are different.


    At first I thought about making separate rails:


    This is definitely gonna work, both devices could share the same ground. Although, the parts I would need for this can't be found easily in my country, and I would need to buy most of them from somewhere else which would take time and money.

    So, going back to my first schematic. Instead of putting the c2000 before, I would put it after the ampop. But I would have to use a battery to bring up the voltage to 5V (I have a 2.4V battery so it would work) Something like this.


    Or maybe a different approach. Back to my 1st schematic, what if I make an unbalanced voltage divider?


    One last idea would be that I could use two 9V battery and use LM7805 to get 5V, followed by LM317 to get 2.5V and same thing to get the - 2.5V. But I don't know if that would be a good approach, even though I don't have to make it work for a long time straight. Just 10 minutes would do.

    Any suggestions??
  2. crutschow


    Mar 14, 2008
    I would go with your last approach using two batteries, one for the positive voltages and one for the negative.
    Otherwise it's difficult to get 5V and ±2.5V from a single battery without using a switching regulator.
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012