Datasheet

USB251xB/xBi
DS00001692C-page 12  2010 - 2015 Microchip Technology Inc.
3.3 Pin Descriptions (Grouped by Function)
An N at the end of a signal name indicates that the active (asserted) state occurs when the signal is at a low voltage
level. When the N is not present, the signal is asserted when it is at a high voltage level. The terms assertion and nega-
tion are used exclusively in order to avoid confusion when working with a mixture of active low and active high signals.
The term assert, or assertion, indicates that a signal is active, independent of whether that level is represented by a high
or low voltage. The term negate, or negation, indicates that a signal is inactive.
TABLE 3-2: USB251XB/XBI PIN DESCRIPTIONS
Symbol
Buffer
Type
Description
UPSTREAM USB 2.0 INTERFACES
USBDM_UP
USBDP_UP
IO-U USB Data: connect to the upstream USB bus data signals (host, port, or upstream
hub).
VBUS_DET I Detect Upstream VBUS Power: detects the state of the upstream VBUS power.
The hub monitors VBUS_DET to determine when to assert the internal D+ pull-up
resistor: (signaling a connect event).
When designing a detachable hub, this pin should be connected to VBUS on the
upstream port via a 2:1 voltage divider. Two 100 k
 resistors are suggested.
For self-powered applications with a permanently attached host, this pin must be
connected to a dedicated host control output, or connected to the 3.3 V domain
that powers the host (typically VDD33).
DOWNSTREAM USB 2.0 INTERFACES
USBDP_DN[x:1]/P
RT_DIS_P[x:1]
IO-U Hi-Speed USB Data: connect to the downstream USB peripheral devices attached
to the hub’s port. To disable, use a 10 k
 pull-up resistor to 3.3 V.
USBDM_DN[x:1]/P
RT_DIS_M[x:1]
Downstream Port Disable Strap Option: when enabled by package and
configuration settings (see Table 5-1 on page 19), this pin is 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 for the
corresponding port number(s). See Section 3.3.1, on page 14 for pull up details.
PRTPWR[x:1]/ O12 USB Power Enable: enables power to USB peripheral devices downstream.
BC_EN[x:1] IPD Battery Charging Strap Option: when enabled by package and configuration
settings (see Table 5-1), the pin will be sampled at RESET_N negation to
determine if ports [x:1] support the battery charging protocol. When supporting the
battery charging protocol, the hub also supports external port power controllers.
The battery charging protocol enables a device to draw the currents per the USB
battery charging specification. See Section 3.3.1, on page 14 for strap pin details.
1 : Battery charging feature is supported for port x
0 : Battery charging feature is not supported for port x
OCS_N[x:1] IPU Over-Current Sense: input from external current monitor indicating an over-current
condition.
RBIAS I-R USB Transceiver Bias: a 12.0 k
 (+/- 1%) resistor is attached from ground to this
pin to set the transceiver’s internal bias settings.