adafruit learning system ItsyBitsy 32u4 Manual page 5

polarity protection, thermal and current-limit protection.
Low current 3.3V regulator output from chip, for small sensors
For the 3V version:
We have two special pins on the 3V version of this board. There's a VHigh pin, this pin is a power pin whose voltage is
the higher of VBAT and VUSB. We also made the digital #5 pin extra special on this board, it connects to a level shifter
so it is only an output but the output is that 'high logic'. Basically what this means is if you want to drive NeoPixels, a
picky servo, or a high-dropout-voltage LED from this board, and you want a 5V-logic-level output, this pin is the one
you should use!
3.3V power and logic, 8 MHz clock rate, 2KB RAM and 28K FLASH
On-board 3.3V power regulator with 500mA output capability and ultra-low dropout. Up to 6V input, reverse-
polarity protection, thermal and current-limit protection.
Special Vhigh output pin gives you the higher voltage from VBAT or VUSB, for driving NeoPixels, servos, and
other high-current devices. Digital 5 level-shifted output for high-voltage logic level output.
Once headers are installed they can be fitted into 0.6" wide sockets
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