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Running the Propeller Mini (#32150) using a single LiPoly battery — Parallax Forums

Running the Propeller Mini (#32150) using a single LiPoly battery

I have a one-off battery powered Propeller project that has some tight space constraints. The smallest Propeller board is the "Mini" but it requires a Vin of >6.5 V. Since space is at a premium and the LiPoly cells only put out a nominal 3.7 V I would need two cells to power it. The rest of the supporting circuit all uses 3.3 V so I do not need anything beyond this. The Mini board comes with a LM2937IMP voltage regulatorfor the 3.3 V which according to the product data sheet requires 4.75 V as the minimum input (which it gets from the on board 5 V regulator). Would there be any harm in replacing this regulator with an LDO regulator such as the MCP1825S-3302E/DB? With a drop out voltage of 0.21 V it should get me 3.3 V out as long as the LiPoly is putting out more than 3.51 V.

Alternatively, is there any harm to putting the LDO regulator on the battery itself then wiring the 3.3V output directly to the 3.3 V pin on the Mini board?

Comments

  • If you don't need 5v you can connect the battery to the 5v pin. I checked with Parallax and then did this on a project -- the 5v regulator will tolerate this so long as nothing is connected to Vin.
  • JonnyMac wrote: »
    If you don't need 5v you can connect the battery to the 5v pin. I checked with Parallax and then did this on a project -- the 5v regulator will tolerate this so long as nothing is connected to Vin.

    What about the minimum 4.75 V input requirement for the LM2937 regulator? The LiPoly only puts out a nominal 3.7 V (and only does this down to about 80% discharge). I am under the impression there won't be any 3.3 V out until there is at least 4.75 Vin, or is this not the case?
  • In my experience it still works -- you'll need to give it a go with the loads you have on the circuit.
  • JonnyMac wrote: »
    In my experience it still works -- you'll need to give it a go with the loads you have on the circuit.

    Simple enough to try. Thank you!

  • If it doesn't work you might try a 3.3v zener circuit.
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