A friend and I are working on building a smartwatch on a budget, so it’s a (very) low power project, but we are currently having a problem with the power supplying. We already chose this board, because of its size and the BLE chip: RFduino BLE SMT For now on, we are planning to use this battery 500 mAh LiPo battery (approx. 4V at full charge) with this voltage regulator Micrel MIC5209-3.6YS (the board supports 3.6V max.).

But the problem is that the Voltage Regulator will apparently drain by itself too much energy from the battery (by heating), reducing drastically the autonomy.

So we would like to know if you guys can help us, if you can tell us exactly what (type of) regulator would be the best or if we need to find another battery.

  • Duplicate: electronics.stackexchange.com/questions/107827/…
    – jippie
    Commented Apr 24, 2014 at 17:27
  • What does this have to do with Arduino?
    – sachleen
    Commented Apr 24, 2014 at 18:03
  • @sachleen the OP mentioned he is using an Arduino clone, so I guess that's OK for arduino.SE (although I admit this may be borderline)
    – jfpoilpret
    Commented Apr 25, 2014 at 5:36
  • 2
    I don't see any reason to close this question as off-topic. The OP is asking us about dimensioning a battery power supply for an Arduino clone. That's pretty on-topic to me. Just the cross-posting with EE.SE that is not ok.
    – Ricardo
    Commented Apr 25, 2014 at 12:54
  • I've created a meta post to discuss this topic. Please post your opinions in that thread.
    – sachleen
    Commented Apr 25, 2014 at 18:51

1 Answer 1


IGND which is mentioned on page 4 of the datasheet is apparently proportional to the output current. This accounts for about 2-5% of the total current drawn by the regulator, depending on its load. With the maximum voltage drop of 4 - 3.6 = 400mV, a switching regulator will make no real difference. I think your only option is to find another regulator that has better efficiency.

  • Hi, Thank you for your fast answer. I just thought : we can't use a linear regulator because it won't let the current pass through below 3.6V, right ? (the chip works down to 1.9V) So, maybe a switching regulator would be better after all. Perhaps you know a reference of one that would fit our needs ?
    – Black3v3r
    Commented Apr 24, 2014 at 17:40

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