4-Port USB 2.0 Controller

Datasheet

Chapter 1 General Description

The USB20H04 four-port hub controller is fully compliant with the USB 2.0 Specification and does not require firmware development. When connected to a high-speed host, the four downstream facing ports can operate at low-speed (1.5Mb/s), full-speed (12Mb/s), or high-speed (480Mb/s). As required by the USB

2.0Specification, the USB20H04 is fully backward compatible with legacy full-speed hosts. A dedicated Transaction Translator (TT) is available for each downstream facing port. This architecture ensures maximum USB throughput for each connected device when operating with mixed-speed peripherals.

The USB20H04 supports both bus-powered and self-powered configurations. For self-powered operation, an external supply is used to power the downstream facing ports. In bus-powered mode, all power is derived from the upstream facing port and no external power supply is required. An external USB power distribution switch device is used to control VBUS switching to downstream ports, and to limit current and sense over-current conditions.

A default configuration is available in the USB20H04 following a reset. This configuration may be sufficient for some applications when it is desired to save the expense of an EEPROM. The controller may also be configured from a microcontroller or an external EEPROM. When using the microcontroller interface, the USB20H04 appears as an SMBus slave device. The EEPROM interface supports a 2-wire I2C device.

All required resistors on the USB ports are integrated into the USB20H04. This includes all series termination resistors on D+ and D– pins and all required pull-down and pull-up resistors on D+ and D– pins. The over-current sense inputs for the downstream facing ports have internal pull-up resistors.

Throughout this document the upstream facing port of the hub will be referred to as the upstream port, and the four downstream facing ports will be called the downstream ports.

1.1Applications

The Universal Serial Bus (USB) hub may be used in a number of applications:

ƒStandalone hubs

ƒKeyboards

ƒMonitors

ƒMotherboard hubs

ƒDocking stations and port replicators

ƒPrinters and scanners

ƒExternal storage devices

ƒAuxiliary battery docks

SMSC USB20H04

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Revision 1.63 (03-30-07)

DATASHEET