B USB Power
We wanted to make the Feather easy to power both when connected to a computer
as well as via battery. There's two ways to power a Feather. You can connect with a
MicroUSB cable (just plug into the jack) and the Feather will regulate the 5V USB
down to 3.3V. You can also connect a 4.2/3.7V Lithium Polymer (Lipo/Lipoly) or Lithium
Ion (LiIon) battery to the JST jack. This will let the Feather run on a rechargable
battery. When the USB power is powered, it will automatically switch over to USB for
power, as well as start charging the battery (if attached) at 100mA. This happens
'hotswap' style so you can always keep the Lipoly connected as a 'backup' power that
will only get used when USB power is lost.
The above shows the Micro USB jack (left), Lipoly JST jack (top left), as well as the
3.3V regulator and changeover diode (just to the right of the JST jack) and the Lipoly
charging circuitry (to the right of the Reset button). There's also a CHG LED, which will
light up while the battery is charging. This LED might also flicker if the battery is not
connected.
The JST connector polarity is matched to Adafruit LiPoly batteries. Using wrong
polarity batteries can destroy your Feather
The charge LED is automatically driven by the Lipoly charger circuit. It will try to
detect a battery and is expecting one to be attached. If there isn't one it may
flicker once in a while when you use power because it's trying to charge a (non-
existant) battery. It's not harmful, and its totally normal!
©Adafruit Industries
Page 19 of 39