XR22414DS Datasheet, PDF (8/13 Pages) Exar Corporation – USB 2.0 4-Port MTT Hub

XR22414
Applications Information
Functional Description
The XR22414 hub has a multiple transaction translator architecture that provides one transaction translator (TT) for each
of the downstream USB ports. The transaction translators allow the USB 2.0 hub to take incoming high speed packets from
the USB host on the upstream port and translate these commands, if necessary to full or low speed devices on any of the
4 downstream ports. The MTT architecture allows for higher bandwidth as the 4 individual ports are not constrained by a
shared resource.
USB Interface
The hub function of the XR22414 supports one configuration and utilizes the following USB endpoints:
■■ Control endpoint
■■ Status change endpoint
The XR22414 hub may be configured for bus powered mode with a maximum power of 500mA or self-powered mode by
connecting the BUS_PWR# pin to the appropriate logic state. In bus powered mode, downstream ports are limited to low
power (100mA or less). When self-powered, downstream devices can draw up to 500mA on each of the four ports.
USB Vendor ID
Exar’s USB vendor ID is 0x04E2.
USB Product ID
Exar’s USB hub product ID is 0x0414.
Device Reset
The XR22414 has both an automatic power-up reset and an external hardware pin reset. Strapping option for ganged power
enables and global over-current sensing are selected by tying the PWR4# pin to logic ‘0’. This pin is sampled at device reset
and the resulting option selected is set.
USB Suspend
All USB peripheral devices must support the USB suspend mode in bus powered mode. Per USB standard, the XR22414
device will begin to enter the suspend state if it does not detect any activity, (including Start of Frame or SOF packets) on
its USB data lines for 3ms. The peripheral device must then reduce power consumption from VBUS power within the next 7
ms to the allowed limit of 2.5mA for the suspended state. Note that in this context, the “device” is all circuitry (including the
XR22414) that draws power from the host VBUS. Each attached downstream port is also allowed an additional 2.5mA of
suspend current. If no devices are connected to the XR22414 downstream ports, the USB host will suspend the hub.
Individual vs. Ganged Power Control and Global Over-current protection mode
Ganged power control mode is enabled when PWR4# is tied to ground. In this mode only the PWR1# output pin is used
for power control and the remaining PWR# pins are unused and should be left unconnected. Global over-current protection
mode is also enabled when PWR4# is tied to ground. In this mode only OVC1# input pin is used for current sensing and
the remaining OVC# pins should be connected to ground. Figure 1 depicts ganged power control / global over-current
protection. Figure 2 depicts individual mode power and over-current modes for ports 1 and 2 (repeat for ports 3 and 4).
Polymeric PTC
5V
2A
OVC1#
OVC2#
OVC3#
OVC4#
XR22414
PWR1#
PWR2#
PWR3#
PWR4#
To VBUS
input of all
downstream
devices
Figure 1: Ganged Power Control and Global Over-Current Protection Mode
REV1A
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