USB2503 datasheet(35/46 Pages) SMSC

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USB 2.0 High-Speed 4-Port Hub Controller

Datasheet

SMSC USB2514

Revision 1.92 (05-08-07)

DATASHEET

The Amber and Green LED pins are sampled after RESET_N negation, and the logic values are used

to configure the hub if the internal default configuration mode is selected. The implementation shown

below (see Figure 4.3) shows a recommended passive scheme. When a pin is configured with a “Strap

High” configuration, the LED functions with active low signalling, and the PAD will “sink” the current

from the external supply. When a pin is configured with a “Strap Low” configuration, the LED functions

with active high signalling, and the PAD will “source” the current to the external LED.

Figure 4.3 LED Strapping Option

4.7

Reset

There are two different resets that the Hub experiences. One is a hardware reset (either from the

internal POR reset circuit or via the RESET_N pin) and the second is a USB Bus Reset.

4.7.1

Internal POR Hardware Reset

All reset timing parameters are guaranteed by design.

4.7.2

External Hardware RESET_N

A valid hardware reset is defined as assertion of RESET_N for a minimum of 1us after all power

supplies are within operating range. While reset is asserted, the Hub (and its associated external

circuitry) consumes less than 500

μA of current from the upstream USB power source.

Assertion of RESET_N (external pin) causes the following:

1. All downstream ports are disabled, and PRTPWR power to downstream devices is removed.

2. The PHYs are disabled, and the differential pairs will be in a high-impedance state.

3. All transactions immediately terminate; no states are saved.

4. All internal registers return to the default state (in most cases, 00(h)).

5. The external crystal oscillator is halted.

6. The PLL is halted.

7. LED indicators are disabled.

The Hub is “operational” 500

μs after RESET_N is negated.

Once operational, the Hub immediately reads OEM-specific data from the external EEPROM (if the

SMBus option is not disabled).

HUB

100K

Strap Low

LED

100K

Strap High

LED

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