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Re: [tracker2] OTUSB running at 3.3v

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  • Scott Miller
    It should be fine at 3.3v. If you ve got a v1.2 board, keep in mind that there s a diode there (D4 I think) that separates regulator power and USB power, so
    Message 1 of 2 , Dec 31, 2011
      It should be fine at 3.3v. If you've got a v1.2 board, keep in mind
      that there's a diode there (D4 I think) that separates regulator power
      and USB power, so you've got a voltage drop equal to Vf on one of those
      diodes. If your supply is exactly 3.3v, you'd probably want to bypass
      that or it'll be too low.

      Everything else should be OK. ADC readings are scaled based on the
      internal band-gap reference so they should still be accurate.

      Scott

      On 12/30/2011 10:04 PM, Matthias Granberry wrote:
      > I'm considering using an OTUSB for a high-altitude balloon launch
      > project and most of the payload will be powered at 3.3v, including the
      > GPS module. A quick look at the schematic and parts list makes me think
      > that everything should work at 3.3v as long as the USB connector is
      > never plugged in while the GPS is connected.
      >
      > Ideally I would remove the LM7805 and substitute an LDO 3.3v regulator
      > in its place and cut the USB +5v trace green-wire it to the regulator
      > input.
      >
      > Has anyone tried anything similar? Should I just break down and use
      > 5v-3.3v level shifters and run the GPS off of a separate power supply?
      >
      > Thanks,
      > Matthias
      >
      >
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