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Using TUSB2046B as an onboard hub. No power management.

Zachery Littell
Prodigy 80 points
Other Parts Discussed in Thread: TPS2044, TUSB2046B

The datasheet does not mention much on using the chip this way, but I am wanting to use this IC to bring together a few usb devices on a single PCB into one connector.  Each device is obviously self-powered on the board since it is all the same power source.  My question is how do I wire the corresponding power management ports.  My goal is to get rid of the TPS IC.  I see one schematic in the datasheet that show !OVRCUR1-4 tie high to 3.3 and !PWRON1-4 left floating.  Is this the correct setup for what I am looking to do?

-Zack-

  • 0
    TI__Mastermind 36085 points

    Hello Zaxhery,

    Both terminals are used as a power managers, as a response of a possible excess of drawn current by the downstream ports.Therefore if you are providing an external power source, You can disable the effect of these terminals (OVRCUR tied to 3.3V and PWRON disconnected).

    Here is a brief explanation of the terminal

    -----

    Configuring the GANGED input determines the power switching and overcurrent 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 terminal. Upon detecting
    any overcurrent conditions, the power-management device sets the corresponding OVRCUR terminal of the
    TUSB2046B to a logic low. If GANGED is high, all PWRON outputs switch together and if any OVRCUR is
    activated, all ports transition to the power-off state. If GANGED is low, the PWRON outputs and OVRCUR inputs
    operate on a per-port basis.

    OVRCUR1-4:

    OVRCUR1–OVRCUR4 are active low. For per-port overcurrent detection, one overcurrent input is available for each of the four downstream ports. In the ganged mode, any OVRCUR input may be used and all OVRCUR terminals must be tied together. OVRCUR terminals are active low inputs with noise filtering logic.

    PWRON1 –4:

    Power-on/-off control signals. PWRON1–PWRON4 are active low, push-pull outputs. Push-pull outputs eliminate the pullup resistors which open-drain outputs require. However, the external power switches that connect to these terminals must be able to operate with 3.3-V inputs because these outputs cannot drive 5-V signals.

    -----

    Information extracted and available on the TUSB2046's Datasheet
    http://www.ti.com/lit/ds/symlink/tusb2046b.pdf

    Regards,

    Diego.

  • 0 in reply to Diego Cortes
    Prodigy 30 points

    Hello Diego, 

    I have a closely related question.  We are doing almost exactly the same thing as Zack.  

    Is it OK to tie the unused OVRCUR terminals directly to the 3.3V, or should 15k resistors (approx) be used to do so?  I have seen it suggested here both ways.  I prefer to omit the resistors if there is no reason to use them.  Thanks.

    Terence.

  • 0 in reply to Terence Brennan
    TI__Mastermind 36085 points

    Hello Terence,

    You can omit these resistors  and tie the OVRCUR terminals to 3.3, indeed there is an example of this implementation on the reference schematic (2046B - RefSch - HIbonMthrBrd).

    http://www.ti.com/litv/zip/sllr048

    Regards,

    DIego.