help power an Arduino with a regulated 3,3v (using lipo)

Hi everyone,

I've made and standalone Arduino uno to interface with a Nokia 5110 display. I'm powering the circuit with a lipo battery directly, I have 3,85v now, but if I charge it, I will have 4,2v +/-

The maximum voltage for the display it is 3.3v, so it will be risky having 4,2v.

which is the best way to regulate the power to 3.3v with a Lipo? I'm thinking in a zener diode, what do you think? (the lm 1117 for example needs an input of at least 4,5v)

Regards

A voltage regulator with a lower dropout voltage. They’re pretty common.

I use this one a lot: http://uk.farnell.com/on-semiconductor/ncp4589dsq33t1g/ldo-300ma-3-3v-tri-5sc70/dp/1885143

With just 230mV dropout voltage it will run off between 3.53V and 5.25V. Although it’s rated at 300mA they do get hot at higher currents, but as they are so small and cheap I tend to use multiple ones in a single circuit - split the power into domains and balance the load accordingly.

You can get higher power ones in bigger packages, such as the MCP1824: http://uk.farnell.com/microchip/mcp1824st-3302e-db/ic-ldo-3-3v-300ma-sot-223-3/dp/1578379 with just a 200mV dropout voltage and the same 300mA. The bigger package with tab means better heatsinking, so it won’t get as hot. Also it’s easier to hand solder than an SC-70, although I have in the past done SC-70 by hand :wink:

Thank you very much, I've already order a couple of MCP1824 samples on microchip website. :D