Datasheet

VDD is the 3.3V logic power. This must be 3 or 3.3V

VBAT is the input to the charge pump. If you use the charge pump, this must be 3.3V to 4.2V

VCC is the high voltage OLED pin. If you're using the internal charge pump, this must be left unconnected. If

you're not using the charge pump, connect this to a 7-9V DC power supply.

For most users, we suggest connecting VDD and VBAT together to 3.3V and then leaving VCC unconnected.