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TUSB8041: TUSB8041 Schematic check for Customer

Sulyn ZHANG
Expert 8700 points
Part Number: TUSB8041
Other Parts Discussed in Thread: AM5706

Hi Team,

My customer is using TUSB8041 to connect to AM5706, the potential volume is big. In fact, customer just need USB2.0, but we only have USB3.0 and USB1.1, so we penetrate TUSB8041. Can you help double check the schematic, thanks for the support!

At the same time, two important question need douoble confirm:

1. Pls also help double confirm R1109,C819,R1111 value? It seems some difference between datasheet and our reference schematic. Need expert help confirm it as well.

2. For each port, customer don't use the 5V VBUS, is this ok(If slave already powered itself)?

AM5706 _ P11-USB.pdf

 Best regards,

Sulyn

  • 0
    TI__Guru 60865 points
    Hi Sulyn,

    Feedback:

    R1109 should be 10K
    C819 looks ok, but may need to be adjusted depending on the voltage ramp timing in the system
    TEST pin should be pulled low
    Are the downstream ports permanently connected to devices?
    Functionally this looks ok, but if the customer is interested in a USB-IF logo they would need to:
    - mark the permanently connected ports via EEPROM
    - set FULLPWRMGMTZ high since they do not implement power management
    - implement overcurrent reporting

    Regards,
    JMMN
  • 0 in reply to JMMN
    TI__Expert 8700 points

    Hi JMMN,

    Thanks for the support! All the slave may need plug in/out, not permanently connected to TUSB8041. So any problem for this? Another question from customer is, why the R1109,C819,R1111 parameters value in datasheet and Reference schematic as below are now same? Any special consideration for the difference?

     

    Best regards,

    Sulyn

  • 0 in reply to Sulyn ZHANG
    TI__Guru 60865 points
    Hi Sulyn,

    Which reference schematic is different from the datasheet? I don't recognize the document. Those component values can vary based on application, but the ones in the datasheet are the standard defaults. It is ok functionally for the downstream ports to be USB 2.0 only, but if the application is to be USB-IF compliant, they expect the exposed ports of a USB 3.0 capable hub to support USB 3.0.

    Regards,
    JMMN
  • 0 in reply to JMMN
    TI__Expert 8700 points

    Hi JMMN,

    Thanks for the support! The reference schematic I mentioned is showed in below link:

    http://www.ti.com/tool/TIDEP0046

    As you can open it see the schematic in it. The pull down resistor on USB_VBUS pin is 16kohm here but not 10kohm showed in datasheet. And also the

    USB_R1 here used is 8.25kohm but not 9.53kohm showed in datasheet, so why are they? Any special consideration or application requirement to make them different with datasheet's requirement? Customer want to know, why and which they need to follow?

    BTW, based on customer's schematic as below, can they connect 4 USB2.0 devices and work normally? All these 4 USB2.0 devices may be plug in/out, not permanently connected. So if the schematic looks ok for above application requirement? Any software consideration for to realize this application requirement if needed?

    Best regards,

    Sulyn

  • 0 in reply to Sulyn ZHANG
    TI__Expert 8700 points

    Hi JMMN,

    Sorry, I missed customer's schematic. See below, thanks.

    4251.AM5706 _ P11-USB.pdf

    Best regards,

    Sulyn

  • 0 in reply to Sulyn ZHANG
    TI__Guru 60865 points

    Hi Sulyn,

    Ok, this reference design was done by a different team specifically for the Sitara processor.  The 16K resistor on USB1_DRVVBUS signal is because the USB1_DRVVBUS is a 3.3V signal instead of the typical 5V VBUS input.  The increased capacitor on GRSTz is likely to address a longer voltage ramp time in the system and the lower USB_R1 value will increase the USB 2.0 drive strength to increase eye height to overcome longer PCB routing / additional devices in the trace.

    Since the customer application uses the USB1_DRVVBUS signal to drive USB_VBUS, the R1109 should be 16K, the other two components will vary on the customer layout.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 8700 points
    Hi JMMN,
    Thanks for the support. Would you help check below questions from customer, thanks:
    1. If All 4 USB downstream ports are USB2.0, Can TUSB8041 upstream port work in USB3.0(use the USB_SSxxx_UP signals but not USB_Dx_UP signals) or it also work in the USB2.0? (Note, Controller in Process can support USB3.0)
    2. If some USB downstream port work in USB2.0 and some in USB3.0, the upstream will definitely work in the USB3.0, correct?

    Best regards,
    Sulyn
  • 0 in reply to Sulyn ZHANG
    TI__Guru 60865 points
    Hi Sulyn,

    The TUSB8041 will connect at both USB 3.0 and USB 2.0 speeds upstream simultaneously, but USB 2.0 traffic is always routed over the USB 2.0 connection and USB 3.0 traffic is routed over the USB 3.0 connection. There is no translation between the buses.

    1. Yes, it will connect at USB 3.0 but no data will be sent over USB 3.0 if the downstream ports are all USB 2.0.
    2. Yes, this is correct.

    Regards,
    JMMN