Datasheet
Table Of Contents
- Chapter 1 USB251x Hub Family Differences Overview
- Chapter 2 General Description
- Chapter 3 Acronyms
- Chapter 4 Block Diagram
- Chapter 5 Pin Descriptions
- Chapter 6 LED Usage Description
- Chapter 7 Battery Charging Support
- Chapter 8 Configuration Options
- Chapter 9 DC Parameters
- 9.1 Maximum Guaranteed Ratings
- 9.2 Operating Conditions
- Figure 9.1 Supply Rise Time Model
- Table 9.1 DC Electrical Characteristics (continued)
- Table 9.2 Supply Current Unconfigured: Hi-Speed Host (ICCINTHS)
- Table 9.3 Supply Current Unconfigured: Full-Speed Host (ICCINTFS)
- Table 9.4 Supply Current Configured: Hi-Speed Host (IHCH1)
- Table 9.5 Supply Current Configured: Full-Speed Host (IFCC1)
- Table 9.6 USB251x/xi/xA/xAi Supply Current Suspend (ICSBY)
- Table 9.7 USB251xB/xBi Supply Current Suspend (ICSBY)
- Table 9.8 USB251x/xi/xA/xAi Supply Current Reset (ICRST)
- Table 9.9 USB251xB/xBi Supply Current Reset (ICRST)
- Table 9.10 Pin Capacitance for USB251x, USB251xi, USB251xA, USB251xAi
- Table 9.11 Pin Capacitance for USB251xB and USB251xBi
- 9.2.1 Package Thermal Specifications
- Chapter 10 AC Specifications
- Chapter 11 Package Outlines

USB 2.0 Hi-Speed Hub Controller
Datasheet
SMSC USB251x 33 Revision 1.1 (04-26-10)
DATASHEET
Chapter 8 Configuration Options
8.1 Hub
SMSC’s USB 2.0 hub is fully specification compliant to the Universal Serial Bus specification, version
2.0, April 27, 2000 (12/7/2000 and 5/28/2002 Errata). Please reference Chapter 10 (Hub specification)
for general details regarding hub operation and functionality.
The hub provides 1 Transaction Translator (TT) that is shared by both downstream ports (defined as
Single-TT configuration), The TT contains 4 non-periodic buffers.
8.1.1 Hub Configuration Options
The SMSC hub supports a large number of features (some are mutually exclusive), and must be
configured in order to correctly function when attached to a USB host controller. There are three
principal ways to configure the hub: SMBus, EEPROM, or by internal default settings (with or without
configuration option over-rides). In all cases, the configuration method will be determined by the
CFG_SEL[2], CFG_SEL[1] and CFG_SEL[0] pins immediately after RESET_N negation. Please refer
to Table 8.1, "Hub Configuration Options" for more information.
8.1.2 SMBus or EEPROM Interface
Table 8.1 Hub Configuration Options
CFG_SEL[2] CFG_SEL[1] CFG_SEL[0] DESCRIPTION
0 0 0 Internal Default Configuration without any over-rides
Strap options enabled
Self-powered operation enabled
LED mode = Speed (when available on package)
Individual power switching
Individual over-current sensing
0 0 1 Configured as an SMBus slave for external download of
user-defined descriptors
Strap options disabled
All settings are controlled by registers as set by the user
0 1 0 Internal Default Configuration
Strap options enabled
Bus-powered operation
LED mode = USB (when available on package)
Individual power switching
Individual over-current sensing
01 12-Wire I
2
C EEPROMS are supported
Strap options disabled
All settings are controlled by registers as set by the user