1.6 USB Transceiver
The MCP2222 includes an integrated, on-chip USB 2.0 full-speed transceiver connected internally to the USB module.
When VDD is supplied from a 5V source, the internal 3.3V regulator powers the USB transceiver, and VUSB pin should be bypassed with a ceramic capacitor.
When VDD is supplied from a 3.3V source, the VUSB pin must be externally connected to the 3.3V supply.