CPU Features Operating voltage – VDD (MCU) fSYS=6MHz: 2.2V~5.5V fSYS=12MHz: 2.7V~5.5V – VDD (USB Mode) fSYS=6MHz/12MHz: 2.7V~5.5V fSYS=16MHz: 4.5V~5.5V Up to 0.25us