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SMPS 2.5V(2xAA) to 3.3V — Parallax Forums

SMPS 2.5V(2xAA) to 3.3V

FredBlaisFredBlais Posts: 370
edited 2010-09-25 23:43 in Robotics
Does anybody here have some experience with SMPS? I know that I need a boost converter for a handheld application, but I'm not quite sure where to get information on this. I estimated the current consumption to 200mA peak, 100mA normal. If some of you have schematics or advice, it would be appreciated. I would also like to know which chips are better/easier for this.

Fred

Comments

  • LeonLeon Posts: 7,620
    edited 2010-09-24 22:52
    Try Nat Semi. They have on-line design tools that makes things quite easy.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-09-24 23:34
    With such a modest current requirement, a switched capacitor doubler like the LM2662, followed by a linear post regulator, may be the simplest route to get what you want.

    -Phil
  • FredBlaisFredBlais Posts: 370
    edited 2010-09-25 19:01
    I have these information for duracell copper top battery

    1A continuous from the battery = 1h20 estimated battery life
    0.75A = 2h15
    0.5A = 4h
    0.25A = 9h

    Option 1 : voltage doubler and ldo regulator
    if I have let's say 140mA continuous from the system, the ldo will dissipate 2(2*1.5v) = 6 volts * .140 = 840mW. The datasheet for the voltage doubler says that the efficiency is about 85%, so I suppose the total power is about 1W. So the battery current is about 1W/3V = 333 mA... so by extrapolation I get about 7h. Does my maths make sense?

    Option 2 :
    I found the L6920D from ST, it is a one chip solution, easier than I thought!
    SMPS.png?psid=1
  • AleAle Posts: 2,363
    edited 2010-09-25 23:43
    I Would use a switching Regulator like the TPS62070. it is Small SOT-23 and requires an Inductur and a Couplet of capacitors. This iPad Drives me Nutts!
    Scratch that, the Device you selected is just fantastic, the Package is a 0.65 pitch One, Quiite Small.
  • AleAle Posts: 2,363
    edited 2010-09-25 23:43
    I Would use a switching Regulator like the TPS62070. it is Small SOT-23 and requires an Inductur and a Couple of capacitors. This iPad Drives me Nutts!
    Scratch that, the Device you selected is just fantastic, the Package is a 0.65 pitch One, Quite Small.
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