Information

3.9.1.2.1 AA/AAA cells power supply
The chip can be powered by two AA/AAA cells. In this case, the MCU is powered
through VDD which is within the 1.8 to 3.0 V range. After USB cable insertion is
detected, the USB regulator is enabled to power the USB transceiver.
USB
Regulator
USB
XCVR
USB
Controller
USB0_DP
USB0_DM
VDD
VOUT33
VREGIN
TYPE A
D+
D-
VBUS
2 AA Cells
Cstab
To PMC and Pads
Chip
Figure 3-49. USB regulator AA cell usecase
3.9.1.2.2 Li-Ion battery power supply
The chip can also be powered by a single Li-ion battery. In this case, VOUT33 is
connected to VDD. The USB regulator must be enabled by default to power the MCU.
When connected to a USB host, the input source of this regulator is switched to the USB
bus supply from the Li-ion battery. To charge the battery, the MCU can configure the
battery charger according to the charger detection information.
Communication interfaces
K20 Sub-Family Reference Manual, Rev. 6, Nov 2011
134 Freescale Semiconductor, Inc.