Highly Integrated Full Featured Hi-Speed USB 2.0 ULPI Transceiver
Datasheet
Note: The IdGnd switch has been provided to ground the ID pin for future applications.
5.6.2
VBUS Monitor and Pulsing
The USB3320 includes all of the VBUS comparators required for OTG. The VBUSVld, SessVld, and
SessEnd comparators shown in Figure 5.11 are fully integrated into the USB3320. These comparators
are used to monitor changes in the VBUS voltage, and the state of each comparator can be read from
the USB Interrupt Status register.
The VbusVld comparator is used by the Link, when configured as an A device, to ensure that the
VBUS voltage on the cable is valid. The SessVld comparator is used by the Link when configured as
both an A or B device to indicate a session is requested or valid. Finally the SessEnd comparator is
used by the B-device to indicate a USB session has ended.
Also included in the VBUS Monitor and Pulsing block are the resistors used for VBUS pulsing in SRP.
The resistors used for VBUS pulsing include a pull-down to ground and a pull-up to VDD33.
In some applications, voltages much greater than 5.5V may be present at the VBUS pin of the USB
connector. The USB3320 includes an overvoltage protection circuit that protects the VBUS pin of the
USB3320 from excessive voltages as described in Section 5.6.2.6, and shown in Figure 5.11.
~
~
VDD33
ChrgVbus
0.5V
SessEnd
en
SessEnd Rise or
SessEnd Fall
SessValid
VBUS
Overvoltage
Protection
1.4V
VBUS
To USB Con.
RVBUS
VbusValid
4.575V
en
DischrgVbus
VbusValid Rise or
VbusValid Fall
[0, X]
[1, 0]
[1, 1]
RXCMD VbusValid
EXTVBUS (logic 1)
IndicatorComplement
[UseExternalVbusindicator, IndicatorPassThru]
SMSC PHY
~
~
Figure 5.11 USB3320 OTG VBUS Block
SessEnd Comparator
5.6.2.1
The SessEnd comparator is designed to trip when VBUS is less than 0.5 volts. When VBUS goes
below 0.5 volts the USB session is considered to be ended, and SessEnd will transition from 0 to 1.
The SessEnd comparator can be disabled by clearing this bit in both the USB Interrupt Enable Rising
and USB Interrupt Enable Falling registers. When disabled, the SessEnd bit in the USB Interrupt Status
register will read 0. The SessEnd comparator trip points are detailed in Table 4.7.
Revision 1.0 (07-14-09)
SMSC USB3320
DATA3S6HEET
SMSC [ SMSC CORPORATION ]
