Exchange current for Voltage

Discussion in 'The Projects Forum' started by czwick, Jul 4, 2012.

  1. czwick

    Thread Starter New Member

    Jul 3, 2012

    I'm trying to power a microcontroller (MSP430G2553) which requires ~1.8V and less than 300uA.

    However, my power supply (which is non-negotiable) supplies a variable amount of voltage depending on the load. If a 3.3kOhm resistor is put across it, it provides 1.68V. 1kOhm: 880mV and 10kOhm: 2.16V, etc

    I am wondering if there is a simple and easy way to convert some of my current to voltage since I need a higher voltage but can get away with a lower current. I'd really prefer not to use any additional components besides the basics...(like the 78xx)

    Thanks so much!
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    Power off. Connect the micro to the supply and mount a series R combination (trimpot + fixed resistor) in parallel with the supply and micro. Power on. Adjust the trimpot to give you the required voltage at the micro. If the micro current is fairly stable with micro function then the supply should hold up OK. I'd suggest you'd also need a parallel decoupling capacitor if the micro doesn't already have one built in. You could start [say] with a 20k trimpot and a 3k3 resistor for the series R combination. If the trimpot 'runs out' of adjustment before you get down to the required voltage, decrease the series fixed resistance and try again.