USB2504/USB2504A
DS000002250A-page 4 2007 - 2016 Microchip Technology Inc.
1.0 INTRODUCTION
The Microchip 4-Port Hub is fully compliant with the USB 2.0 Specification and will attach to a USB host as a Full-Speed
Hub or as a Full-/High-Speed Hub. The 4-Port Hub supports Low-Speed, Full-Speed, and High-Speed (if operating as
a High-Speed Hub) downstream devices on all of the enabled downstream ports.
A dedicated Transaction Translator (TT) is available for each downstream facing port. This architecture ensures maxi-
mum USB throughput for each connected device when operating with mixed-speed peripherals.
The Hub works with an external USB power distribution switch device to control V
BUS
switching to downstream ports,
and to limit current and sense over-current conditions.
All required resistors on the USB ports are integrated into the Hub. 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 down-
stream facing ports will be called the downstream ports.
1.1 OEM Selectable Features
A default configuration is available in the USB2504/USB2504A following a reset. This configuration may be sufficient
for some applications. Strapping option pins make it possible to modify a limited sub-set of the configuration options.
The USB2504/USB2504A may also be configured by an external EEPROM or a microcontroller. When using the micro-
controller interface, the Hub appears as an SMBus slave device. If the Hub is pin-strapped for external EEPROM con-
figuration but no external EEPROM is present, then a value of ‘0’ will be written to all configuration data bit fields (the
hub will attach to the host with all ‘0’ values).
The 4-Port Hub supports several OEM selectable features:
• Operation as a Self-Powered USB Hub or as a Bus-Powered USB Hub.
• Operation as a Dynamic-Powered Hub (Hub operates as a Bus-Powered device if a local power source is not
available and switches to Self-Powered operation when a local power source is available).
• Multiple Transaction Translator (Multi-TT) or Single-TT support.
• Optional OEM configuration via I
2
C EEPROM or via the industry standard SMBus interface from an external
SMBus Host.
• Port power switching on an individual or ganged basis.
• Port over-current monitoring on an individual or ganged basis.
• LED indicator support.
• Compound device support (port is permanently hardwired to a downstream USB peripheral device).
• Hardware strapping options enable configuration of the following features.
- Non-Removable Ports
- Port Power Polarity (active high or active low logic)
- Port Disable
- LED support
- MTT enable
- Ganged Vs Port power switching and over-current sensing
