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TUSB4041I: Clock Crystal Question

Mert Kantarcioglu
Intellectual 390 points
Part Number: TUSB4041I
Other Parts Discussed in Thread: TPS2052C

Hi,

I would like to design a 10 port USB hub with TUSB4041I with 2 tiers. I have some design questions below to be answered.

At TIER1 there is a TUSB4041I and I will connect its downstream ports to TIER2 (2xTUSB4041I, 1xTUSB4020BI and 1xMCU via FTDI Serial Converter chip)

  1. Can I use same clock crystal for TIER1 and TIER2 hubs (3xTUSB4041I and 1xTUSB4020BI) or every hub should have different clock crystals?
  2. I am planning to use self powered hub configuration for TIER2, can I use bus powered for TIER1 and TIER2 Upstream ports or connect to 5VDC in my design?
  3. Should I use OVERCURxz pins for TIER1 hub? What if I have left as unconnected?
  4. Should I take any ESD, EMI protection measures for TIER2 to USB connectors? I think these measures are taken in TUSB4041I, but if you have any suggestion to improve these measures with extra circuit please advice.
  5. I would like to sense OVERCURxz pins for TIER2 with MCU for error reporting. Therefore MCU and Power Switch (TPS2052C) will be connected together. Most probably I will use an isolation circuit to isolate MCU. Do you have any connection measure advice?

Thanks for your support.

  • 0
    TI__Guru 64326 points

    Hi Mert,

    1. Every hub should have it own dedicated crystal.

    2. When using this many hubs it is best to be fully self powered to avoid over current on upstream port.

    3. Tier 1 hub OVERCURxz are not required to be used and can be left unconnected since tier 2 hubs are all self powered.

    4. If additional ESD performance (>4kV HBM) is need devices can always be added to the downstream and upstream port to achieve the desired limits. In addition, ferrite beads and small capacitors on the VBUS lines can help reduce noise and address ESD/EMI concerns. CMC can also be used on the USB 2 bus. Please make sure to select components that will not interfere with signal integrity of the USB2 bus. 

    5. I recommend using OVERCURxz on the Tier2 hubs should be connected to TPS2052C such that the USB Hub can report this to the USB Host. If you are planning to have the MCU report these events on a per port basis then OVERCURxz can be tied high.