Moteino minimum recommended VIN

Started by hakunin, November 18, 2016, 02:48:29 PM

hakunin

Hello,
I am a bit confused about the recommended minimum V_IN for the Moteino.
On  https://lowpowerlab.com/guide/moteino/specifications/ is 3.6V, on the moteino pinout picture is 3.3V, on the same page https://lowpowerlab.com/shop/product/99 of the pic under "What is it" is 3.5V.
If I check the MCP1703 Datasheet, I see V_IN = V_OUT + V_Dropout = 3.3V + 0.525V (Typ V Dropout with I_OUT= 250mA and V_OUT= 3.3V) = 3.825V. From the graphs, I don't see much change even when drawing less current.
If I power my moteino with 3.7 Li-Ion, after it goes under 3.8V, will the Moteino have less then 3.3V on the 3.3V rail? Are we "speculating" on the fact, the the Atmega can run also with less then 3.0V? But then what about other devices that are connected the the 3.3V rail? They might not work correctly, right?
Thanks for any feedback
Sincerely

Felix

Thanks for pointing out the inconsistencies, motivates me to fix them!
The pinouts are quite old and I have to make new ones.
I fixed the product pages to reflect the spec. It is really around 3.6V but even if you drop below that (ie between 3.3v and 3.6v) the regulator will output 3.3v.
If you drop below 3.3v then the regulator will output that voltage BUT will use a lot more power (I think around 200uA more or so).
Very important to note is that dropout voltage is load dependent so with very light loads it will be a lot less:


hakunin

Thanks Felix for clarifying that!
Awesome Moteino!