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TUSB4041I: Independent Power Supply, effective disregard of power management.

Dean Rossouw
Prodigy 50 points
Part Number: TUSB4041I

I have a design which requires multiple USB 2.0 HS devices, and will be using this device to connect the data lines to a host PC, but will be implementing power supply sources to the connected USB devices that will be independent of the USB bus and the hub ICs. Are there any specific recommendations to disabling/not using any of this ICs power supply/management features (downstream) as to avoid any problems? I have read the datasheets and related application notes, but can not find any information specifically related to this (complete independence). Any help would be most appreciated.

  • 0
    TI__Guru 60870 points
    Hi Dean,

    Make sure the hub is set to report that is does not enable full power management (FULLPWRMGMTz = 1). Also, make sure the overcurrent inputs are not pulled low. To obtain a USB compliance logo, a hub application must have overcurrent reporting enabled, but for a closed system this is not an issue. Also, per the USB specification any hub port that has a permanently connected device should have that port marked as "non-removable". Again, functionally this is not a concern but if USB compliance is required, this would need to be set via I2C EEPROM / SMBUS or efuse.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Prodigy 50 points

    Hi JMMN

    Thank you for your answer.

    I have FULLPWRMGMTz pulled to 3.3v with a 10k resistor and PWRCTL1-4 pulled to GND with 10ks. I have left TEST, USB_VBUS, OVERCUR1z-4z, GANGED, PWRCTL_POL and AUTOENz all N/C. I have also left the SM Bus ports N/C (SMBDAT, SMBCLK, SMBUSz). Can you foresee any issues with that configuration? It is basically what I gathered from the datasheet, but there are one or two (AUTOENz, GANGED) that I was usure what to do with, ie ground or leave N/C. USB compliance is not an issue.

  • 0 in reply to Dean Rossouw
    TI__Guru 60870 points
    Hi Dean,

    I would skip the pulldowns on PWRCTL since the outputs are not being used. The outputs will still drive and you'll have more current draw if they are pulled down, but it isn't a major concern either way. I would also recommend an external pulldown on the TEST pin. It does have an internal pulldown, but this is a pin that if it gets pulled high due to a noise event will cause the hub to stop functioning as a hub and enter test mode, so I would err on the side of caution.

    USB_VBUS is a required input. If the hub doesn't see ~500 mV (the divided down value of 5V VBUS), the hub will not turn function.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Prodigy 50 points

    Hi JMMN

    Thank you for the advice. I have noted your suggested changes. I assume the rest of my intended connections are fine? How much is the acceptable deviation on the 500mV?

    Regards

    Dean

  • 0 in reply to Dean Rossouw
    TI__Guru 60870 points
    Hi Dean,

    The rest of the connections looked acceptable. The USB_VBUS input is made to track a divided down version of VBUS, so Vih (min) would be around 430 mV. The Vih (max) is 1.15V.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Prodigy 50 points

    HI JMMN

    Thank you