GL850 is a 4-port standard Universal Serial Bus (USB) hub controller complies with Universal Serial Bus
Specification Revision 2.0. GL850 can be connected to an USB1.1 host/hub or an USB2.0 host/hub. When
GL850 is connected to an USB1.1 host/hub, it works just like an USB1.1 hub; the upstream port will operate
in full-speed (FS) and the downstream port can operate in full-speed or low-speed (LS). When GL850 is connected to an USB2.0 host/hub, it works as an USB2.0 hub; the upstream port will operate in high-speed (HS) and the downstream port can operate in high-speed, full-speed, or low-speed. The bandwidths of high speed, full speed, and low speed are 480 Mbps, 12 Mbps, and 1.5 Mbps respectively.GL850 embeds an 8-bit RISC processor to manipulate the control/status registers and responds to the requests from USB host. Firmware of GL850 will control its general purpose I/O (GPIO) to access the external
EEPROM and then respond to the host the customized PID and VID configured in the external EEPROM.GL850 responds to the host the default settings in the internal ROM if there exists no external EEPROM.GL850 is designed for customers with much flexibility. Customers can easily design GL850 as 4-port self/bus powered, individual/ganged mode, by setting the I/O pins of GL850 (Ref. to Chapter 5). The more complicated settings such as PID, VID, and number of downstream ports settings are easily achieved by programming the external EEPROM.
TT (transaction translator) is the main traffic control engine in an USB2.0 hub to handle the unbalanced traffic speed between the upstream port and the downstream ports. GL850 adopts single TT architecture, which shares the same TT buffer for all downstream devices.
Each downstream port of GL850 supports two-color (green/amber) status LEDs to indicate normal/abnormal status. The downstream ports of GL850 can be configured as individual mode or gang mode (4 ports as a group) for power management. Gang mode is very helpful for cost consideration, since we can use one poly-fuse, but not expensive power switch chips, to detect over current. GL850 passes the current requirement (< 2.5mA) for bus-power mode when being suspended. The current consumption is smaller than 100mA for the GL850 silicon itself. The above requirements are necessary for a 4-port bus power hub. Under adequate PCB designing, GL850 provide a good choice for customers as a 4-port bus powered hub. Besides, GL850 can switch automatically between self-power mode and bus-power mode
without re-plugging into the PC host. The slew rate control circuits and the power fail detection circuits inside this chip give better ESD and EMI abilities to GL850.
GL850 is designed mainly for stand-alone hub. It can also be integrated into PC motherboard or any other compound devices to support USB hub function.