Datasheet

245
7593L–AVR–09/12
AT90USB64/128
Figure 22-8. Host/OTG application with 5V I/O.
22.3.3 Design guidelines
• Serial resistors on USB Data lines must have 22Ω value (±5%)
• Traces from the input USB receptable (or from the cable connection in the case of a tethered
device) to the USB microcontroller pads should be as short as possible, and follow differential
traces routing rules (same length, as near as possible, avoid vias accumulation)
• Voltage transient / ESD suppressors may also be used to prevent USB pads to be damaged
by external disturbances
•U
cap
capacitor should be 1µF (±10%) for correct operation
• A 10µF capacitor is highly recommended on VBUS line
UDP
UDM
VBUS
UVSS
UID
D-
D+
VBUS
UID
UGND
1µF
External 5.0V
power supply
UCAP
UVCC AVCC VCC
XTAL1 XTAL2 GND GND
UVCON
5V
Rs = 22
Rs = 22