XR22404 Datasheet, PDF (7/14 Pages) Exar Corporation – USB 2.0 4-Port Hub

XR22404
Applications Information
Functional Description
The XR22404 hub has a single transaction translator that allows 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 commands on any of
the 4 downstream ports. Additionally, the XR22404 can provide battery charging on all four downstream ports compatible
with the USB Battery Charging Specification revision 1.1/1.2.
USB Interface
The hub function of the XR22404 supports one configuration and utilizes the following USB endpoints:
■■ Control endpoint
■■ Status change endpoint
The XR22404 hub may be configured for bus powered mode with a maximum power of 500 mA 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 (100 mA or less). When self-powered, downstream devices can draw up to 500 mA 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 0x0404.
Device Reset
The XR22404 has both an automatic power-up reset and an external hardware pin reset. Normal hub operation or charging
mode is sampled on the LED_CTL/CHRGEN pin at device reset. Refer to Table 1 for further description of charging modes.
USB Suspend
All USB peripheral devices must support the USB suspend mode. Per USB standard, the XR22404 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
3 ms. In bus powered mode the peripheral device must then reduce power consumption from VBUS power within the next
7 ms to the allowed limit of 2.5 mA for the suspended state. Note that in this context, the “device” is all circuitry (including
the XR22404) that draws power from the host VBUS. Each attached downstream port is also allowed an additional 2.5 mA
of suspend current. If no devices are connected to the XR22404 downstream ports, the USB host will suspend the hub.
Ganged Power Control and Global Overcurrent Sensing
The OVC# pin is used as a global overcurrent protection input for current sensing. The PWR# pin will be asserted whenever
the OVC# input pin is asserted or the XR22404 device is not yet configured.
REV1A
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