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TUSB8041: downstream power management system

Niranjan Madhavan
Intellectual 605 points
Other Parts Discussed in Thread: TUSB8041

Hi,

I am using TUSB8041 for connectivity of my system. I am using 3 out of 4  ports for communication and 4th port is kept unconnected would be used in future. System is configured to full power management control and individual control power management enabled. 

On port1: I am connecting a USB2.0 device which is not powered from VBUS(externally powered device). So there is only dateline (d+ and d_) is connected. Rest USB 3 pins are not connected. All lines are hardwired in PCB and no connectors for this port. The power management pins are also not required. Can I leave PWERCTL1/BATEN1 unconnected? or Should I ground it? And how about Overcur1z? Currently I am planning to connect to Vdd to keep it active high.

FYI: On port 2 and 3 I am using power switches to control the downstream power and on port 4 all the pins are unconnected. On port 2 and three there would be USB 3 micro B connectors.

  • 0
    TI__Guru 60870 points

    Hi Niranjan,

    If the power management on a port is not used, PWRCTL/BATEN can be left unconnected.  On any exposed port, hubs are required by the USB specification to have the ability to report an overcurrent event.  Functionally, the hub doesn't care as long as a false overcurrent is never reported (use an external pullup).  The rest of the application sounds good.  Please be aware that if you want to receive a USB logo or WHQL certification on your product:  unused ports must be marked as unused using OTP or EEPROM.  Also, permanently connected ports must be marked as non-removable using EEPROM.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Intellectual 605 points
    Thank you for quick reply.
    But this triggered another question. I am not using any EEPROM for currently application. In my understanding, it will not affect any functionality am I right? Do I need to do any extra work (software/hardware) if no EEprom is used?

    And so for getting USBlogo or WHQL we need a configured EEPROM, am I understanding right? I am not sure we need USB logo on our product though! I need to get input from my higher management.
  • 0 in reply to Niranjan Madhavan
    TI__Guru 60870 points
    The TUSB8041 is designed to be used with or without EEPROM. EEPROM just adds configuration capabilities. If your board has room, I would consider putting the SDA / SCL pullups and EEPROM in the design and just not populating them in case your application needs a logo or WHQL certification in the future.