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USB 2.0 Hi-Speed Hub Controller
Datasheet
Revision 1.0 (3-11-09) 22 SMSC USB251x
DATASHEET
5.2 USB251x Pin Descriptions (Grouped by Function)
Table 5.2 USB251x Pin Descriptions
SYMBOL
BUFFER
TYPE DESCRIPTION
UPSTREAM USB 2.0 INTERFACES
USBDM_UP
USBDP_UP
IO-U USB Data
These pins connect to the upstream USB bus data signals (host, port, or
upstream hub).
VBUS_DET I/O12 Detect Upstream VBUS Power
Detects state of Upstream VBUS power. The SMSC hub monitors
VBUS_DET to determine when to assert the internal D+ pull-up resistor which
signals a connect event.
When designing a detachable hub, this pin should be connected to VBUS on
the upstream port via a 2 to 1 voltage divider.
For self-powered applications with a permanently attached host, this pin must
be connected to 3.3 V (typically VDD33).
DOWNSTREAM USB 2.0 INTERFACES
USBDP_DN[x:1]/
PRT_DIS_P[x:1]
IO-U Hi-Speed USB Data
These pins connect to the downstream USB peripheral devices attached to
the hub’s port. To disable, pull up with a 10 K resistor to 3.3 V.
USBDM_DN[x:1]/
PRT_DIS_M[x:1]
Downstream Port Disable Strap Option
If this strap is enabled by package and configuration settings (see Table 8.1,
"Hub Configuration Options"), then this pin will be sampled at RESET_N
negation to determine if the port is disabled.
To disable a port, pull up both PRT_DIS_M[x:1] and PRT_DIS_P[x:1] pins
corresponding to the port numbers.
PRTPWR[x:1] /
BC_EN[x]
O12 USB Power Enable
Enables power to USB peripheral devices downstream.
When PRTPWR_POL pin is unavailable, the hub supports active high power
controllers only.
When PRTPWR_POL pin is available, the active signal level of the PRTPWR
pins is determined by the power polarity strapping function of the
PRTPWR_POL pin.
IPD Battery Charging Strap Option
*This feature is only available on USB251xB/Bi.
If this strap is enabled by package and configuration settings, (see Table 8.1,
"Hub Configuration Options"), this pin will be sampled at RESET_N negation
to determine if ports [x:1] support the battery charging protocol (and thus the
supporting external port power controllers) that would enable a device to draw
the currents per the USB battery charging specification.
BC_EN[x] = 1: Battery charging feature is supported for port x
BC_EN[x] = 0: Battery charging feature is not supported for
port x