USB 2.0 Hi-Speed Hub Controller

Datasheet

Chapter 6 LED Usage Description

6.1LED Functionality

USB2513 and USB2514 (48-pin QFN only) and USB2517/17i SMSC hubs support two different (mutually exclusive) LED modes. The ‘x’ represents the number of downstream ports. The USB mode provides up to 14 LED’s that conform to the USB 2.0 specification functional requirements for Green and Amber LED’s. The LED mode “speed indicator” provides the downstream device connection speed.

6.1.1USB Mode 14-Wire

The LED_A_N[x:1] pins are used to provide Green LED support as defined in the USB 2.0 specification. The LED_B_N[x:1] pins are used to provide Amber LED support as defined in the USB

2.0specification. The USB specification defines the LED’s as port status indicators for the downstream ports. Please note that no indication of port speed is possible in this mode. The pins are utilized as follows:

LED_A_N[x:1] = Port [x:1] green LED

LED_B_N[x:1] = Port [x:1] amber LED

6.1.2LED Mode Speed Indication

The LED_A[x:1]_N pins are used to provide connection status as well as port speed by using dual color LED's. This scheme requires that the LED's be in the same package, and that a third color is produced so that the user perceives both LED's as being driven "simultaneously".

The LED_A[x:1] pins used in this mode are connected to x number of dual color LED’s (each LED pair in a single package). These pins indicate the USB speed of each attached downstream device.

Each dual color LED provides two separate colors (commonly Green and Red). If each of these separate colors are pulsed on and off at a rapid rate, a user will see a third color (in this example, Orange). Using this method, 4 different "color" states are possible (Green, Red, Orange, and Off).

3.3 V

General

 

Purpose

 

Diode

Connection to

other Dual Color

Diodes

D1A (Green LED)Hub LED pin

Current Limiting

Resistor

D1B (Red LED)Figure 6.1 Dual Color LED Implementation Example

SMSC USB251x

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Revision 1.0 (3-11-09)

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