Hi All,
I have a project I am working on where I will be making use of a couple of 3.3V components. (Gyro’s and Acenlerometers). The project is also space/weight critical.
My Question:
Can you run a FEZ Mini from +3.3V supply or does it need +5V? In the documentation it says that the FEZ Mini is 5V Tollerant, but does that mean I can run it from 3.3V or not? This would save a voltage regulator and related components for my Interface board.
Thanks
The mini takes between 5 and 9v in. There is a 3.3v vreg on board. You could connect your 3v supply directly to the output pin of the voltage regulator to bypass this if you wanted.
I don’t have a mini, however on the back of your mini there is a component called IC2. It is at the bottom edge of the board with 3 pins on one side, and 1 tab on the top. The pin closest to the edge of the board should be carrying 5v if you are using USB, and the pin closest to the “www” of the url should have 3.3v. Check this with a multimeter (the big tab should be ground).
If the pin towards the www is 3.3v, connect your 3.3v source here.
By 5v tolerant, it means that the pin can handle you putting 5v into it, for example you have a component that has 5v logic, you don’t need to do anything fancy to drop the voltage down to 3.3v to not blow the MCU up 
There is 3.3V pin on FEZ Mini, connect your regulated 3.3V to that pin 
Yea, I forgot about the 3.3volt regulator chip which would not work if I pushed 3.3volt into The 5V supply. I’ll stick to the 5Volt supply then in case I wreck my mini. Once I’ve got this project going I’ll look into using the USBIzi chips directly rather than start tinkering with my shiny mini board now.