GL850A USB 2.0 Low-Power HUB Controller
USB2.0 HOST/HUB
USPORToperating
in HS signaling
HS vs. HS:
Traffic channel is
routed to REPEATER
HS vs. FS/LS:
Traffic channel
is routed to TT
REPEATER
TT
DSPORT operating
in FS/LS signaling
DSPORT operating
in HS signaling
Figure 5.2 – Operating in USB 2.0 scheme
5.12 DSPORT logic
DSPORT (downstream port) logic implements the control logic defined in section 11.5 of USB specification
Revision 2.0. It mainly manipulates the state machine, the connection/disconnection detection, over current
detection and power enable control, and the status LED control of the downstream port. Besides, it also
output the control signals to the DSPORT transceiver.
5.13 DSPORT Transceiver
DSPORT transceiver is the analog circuit that supports high-speed, full-speed, and low-speed electrical
characteristics defined in chapter 7 of USB specification Revision 2.0. In addition, each DSPORT
transceiver accurately controls its own squelch level to detect the detachment and attachment of devices.
5.2 Configuration and I/O Settings
5.2.1 RESET# Setting
GL850A integrates in the pull-up 1.5KΩ resister of the upstream port. When RESET# is enabled, the
internal 1.5KΩ pull-up resister will be disconnected to the 3.3V power. To meet the requirement (p.141) of
the USB 2.0 specification, pull-up resister should be disconnected while lacking of USB cable power
(Vbus). Therefore, we suggest designing the RESET# circuit as following figure to meet the requirement
mentioned above.
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