Datasheet

186
7799D–AVR–11/10
ATmega8U2/16U2/32U2
20.3 USB Module Powering Options
Depending on the selected target application power supply (V
CC
), the ATmega8U2/16U2/32U2
USB controller requires different powering schemes, see Figure 20-2 on page 186.
Figure 20-2. Operating modes versus frequency and power-supply
20.3.1 Bus Powered device
The following figures show typical implementations for different powering schemes.
Figure 20-3. Typical Bus powered application with 5V I/O
VCC (V)
VCC min
0
3.0
4.0
5.5
USB not operational
USB compliant,
without internal regulator
USB compliant,
with internal regulator
4.5
2.7
Max
Operating Frequency (MHz)
8 MHz
16 MHz
2 MHz
3.6
1µF
UDM
UDP
VBUS
UVSS
UCAP
D-
D+
UVCC
VCC AVCC
UVSS
VSS
XTAL1 XTAL2