at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 672

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

37.4
Figure 37-2. Board Schematic to Interface Device Peripheral
37.4.1
37.4.2
672
Typical Connection
AT91SAM9G20 Preliminary
USB Device Transceiver
VBUS Monitoring
PIO
DDM
DDP
5V Bus Monitoring
The USB device transceiver is embedded in the product. A few discrete components are
required as follows:
VBUS monitoring is required to detect host connection. VBUS monitoring is done using a stan-
dard PIO with internal pullup disabled. When the host is switched off, it should be considered as
a disconnect, the pullup must be disabled in order to prevent powering the host through the pull-
up resistor.
When the host is disconnected and the transceiver is enabled, then DDP and DDM are floating.
This may lead to over consumption. A solution is to enable the integrated pulldown by disabling
the transceiver (TXVDIS = 1) and then remove the pullup (PUON = 0).
A termination serial resistor must be connected to DP and DM. The resistor value is defined in
the electrical specification of the product (R
• the application detects all device states as defined in chapter 9 of the USB specification;
• to reduce power consumption the host is disconnected
• for line termination.
– VBUS monitoring
47 K
27 K
R
R
EXT
EXT
EXT
).
2
3
Connector
Type B
1
4
6384B–ATARM–15-Dec-08