Information

3.9.1.1 USB Wakeup
When the USB detects that there is no activity on the USB bus for more than 3 ms, the
INT_STAT[SLEEP] bit is set. This bit can cause an interrupt and software decides the
appropriate action.
Waking from a low power mode (except in LLS/VLLS mode where USB is not powered)
occurs through an asynchronous interrupt triggered by activity on the USB bus. Setting
the USBTRC0[USBRESMEN] bit enables this function.
3.9.1.2 USB Power Distribution
This chip includes an internal 5 V to 3.3 V USB regulator that powers the USB
transceiver or the MCU (depending on the application).
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 3-42. USB regulator AA cell usecase
Chapter 3 Chip Configuration
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 113