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TUSB8041 datasheet contradiction on PWRCTL_POL pin

Ben Stelle
Intellectual 620 points
Other Parts Discussed in Thread: TUSB8041, TPS2561, TPS2560

Hello, I have found what I think is a contradiction on the datasheet for the TUSB8041.  On page 33 of the datasheet, there is a statement about the reference design shown in the datasheet that says:  "The PWRCTL_POL is pulled down which will result in active high power enable (PWRCTL1, PWRCTL2, PWRCTL3, and PWRCTL4) for a USB VBUS power switch."  However, the pin description on page 7 indicates that a "1 = PWRCTL polarity is active high".  Is this an error of some sort?

I also have a question regarding the use of this part.  I would like to set this up to be a HUB that does not need to be configured, so I think that I need to set it up for I2C mode.  That's easy enough to do, but I am wondering if I have to have a memory device attached or if I can get by without a memory device on the I2C bus.  Can you help with this?

Regards,

Ben

  • 0
    TI__Guru 60870 points

    Hi Ben,


    Yes, that is a typo on page 33.  It was corrected in the commercial version of the datasheet, but it looks like that change did not get ported to the automotive version.

    You want to keep SMBUSz mode disabled (enabling I2C mode) if you are using the default / pin configurations.    The hub will look for an EEPROM and if it doesn't see one, it will configure the device based on the input pins.  If the hub is configured for SMUBS mode, it will not work as a hub until accessed by a SMBUS host.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Intellectual 620 points
    Given that page 33 is a typo, is it also then true that the switches depicted on page 32 must be TPS2560s instead of TPS2561?

    Thanks for clarifying the I2C question. One last question comes to mind. I believe that the reference design in the schematic shows several configuration resistors on pins that have already have internal resistors. Has this been found to be necessary, or are the internal pull resistors strong enough for configuration on reset?

    Regards,

    Ben
  • 0 in reply to Ben Stelle
    TI__Guru 60870 points
    Yes, either the power switches should be TPS2560 or the pulldown on PWRCTL_POL should be unpopulated. The internal pulldowns or pullups are sufficient to set the inputs.

    Regards,
    Julie Nirchi