TUSB2077A

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SLLS414F – MARCH 2000 – REVISED AUGUST 2015

5 Description (Continued)

The EXTMEM pin (pin 47) enables or disables the optional EEPROM interface. When EXTMEM is high, the

vendor and product IDs (VID and PID) use defaults, such that the message displayed during enumeration is

General Purpose USB Hub.

The TUSB2077A supports bus-powered and self-powered modes. External power-management devices, such as

the TPS2044, are required to control the 5-V power source switching (on/off) to the downstream ports and to

detect an overcurrent condition from the downstream ports individually or ganged. An individually port power

controlled hub switches power on or off to each downstream port as requested by the USB host. Also when an

individually port power controlled hub senses an overcurrent event, only power to the affected downstream port

will be switched off. A ganged hub switches on power to all its downstream ports when power must be on for any

port. The power to the downstream ports is not switched off unless all ports are in a state that allows power to be

removed. Also, when a ganged hub senses an overcurrent event, power to all downstream ports will be switched

off.

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