Datasheet

USB 2.0 Hi-Speed Hub Controller

Datasheet

SMSC USB251xB/xBi 23 Revision 2.2 (02-17-12)

DATASHEET

3.3.1.3 LED

If a strap pin’s buffer type is I/O and shares functionality with an LED, the hardware configuration

outlined below must be implemented. The internal logic will drive the LED appropriately (active high or

low) depending on the sampled strap option. Use the Strap High configuration to set the strap option

value to 1 and Strap Low to set the strap option to 0.

Figure 3.6 LED Pin Strap Example

3.4 Buffer Type Descriptions

Table 3.5 Buffer Type Descriptions

BUFFER TYPE DESCRIPTION

I Input

I/O Input/output

IPD Input with internal weak pull-down resistor

IPU Input with internal weak pull-up resistor

IS Input with Schmitt trigger

O12 Output 12 mA

I/O12 Input/output buffer with 12 mA sink and 12 mA source

I/OSD12

Open drain with Schmitt trigger and 12 mA sink. Meets the I

C-Bus

Specification [2] requirements.

ICLKx XTAL clock input

OCLKx XTAL clock output

I-R RBIAS

I/O-U Analog input/output defined in USB specification

HUBHUB

Strap Pin

LED/

Strap High

Strap Pin

LED/

Strap Low

kΩ