TUSB2046A

4-PORT HUB FOR THE UNIVERSAL SERIAL BUS

WITH OPTIONAL SERIAL EEPROM INTERFACE

SLLS404 – DECEMBER 1999

2

POST OFFICE BOX 655303

description (continued)

Configuring the GANGED input determines the power switching and over-current detection modes for the

downstream ports. External power management devices such as the TPS2044 are required to control the 5-V

source to the downstream ports according to the corresponding values of the PWRON pin. Upon detecting any

over-current conditions, the power management device sets the corresponding OVRCUR pin of the

TUSB2046A to a logic low. If GANGED is high, all PWRON outputs switch together and if any OVRCUR is

activated, all ports transition to power off state. If GANGED is low, the PWRON outputs and OVRCUR inputs

operate on a per port basis.

Low EMI emission is achieved because the TUSB2046A is able to utilize a 6 MHz crystal input. Connect the

crystal as shown in Figure 7. An internal PLL then generates the 48 MHz clock used to sample data from the

upstream port and to synchronize the 12 MHz used for the USB clock. If low power suspend and resume are

desired, a passive crystal or resonator must be used. However, a 6-MHz oscillator may be used by connecting

the output to the XTAL1 terminal and leaving the XTAL2 terminal open. The oscillator TTL output should not

exceed 3.6 V.

The EXTMEM pin enables or disables the optional EEPROM interface. When the EXTMEM pin is high, the

product ID (PID) displayed during enumeration is the general-purpose USB hub. For this default, pin 5 is

disabled and pin 6 functions as the GANGED input pin. If custom PID and Vendor ID (VID) descriptors are

desired, the EXTMEM pin must be low (EXTMEM = 0). For this configuration, pin 5 and pin 6 function as the

EEPROM interface with pin 5 and pin 6 functioning as the EECLK and EEDATA, respectively. See Table 1 for

a description of the EEPROM memory map.

Other useful features of the TUSB2046A include a package with a 0.8 mm pin pitch for easy PCB routing and

assembly, push-pull outputs for the PWRON pins eliminate the need for pullup resistors required by traditional

open collector I/Os, and OVRCUR pins have noise filtering for increased immunity to voltage spikes.