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TUSB8041: The data rate quesion for TUSB8041

Mickey Zhang
Genius 12080 points

Part Number: TUSB8041

Hi team,

The customer uses TUSB8041. I would like to get which parameters can determine  the USB data rate.

Please check the attach. Would you explain what the data ratesthat is the red circle which is in the attach

for these USB hub?

  • 0
    TI__Guru 64326 points

    Mickey,

    The USB data rate is dictated by the speed of the source primarily (personal computer in the figure) and influenced by how often each USB device in the red circles occupy the USB bus. The max achievable data rate for the USB 2.0 connections is 480 Mbps and the for USB 3.0 connections it is 5Gbps.

  • 0 in reply to Malik Barton57
    TI__Genius 12080 points
    Hi Malik,

    Would you send me an example to explain that you said"The USB data rate is dictated by the speed of the source primarily (personal computer in the figure) and influenced by how often each USB device in the red circles occupy the USB bus"? What is the "each USB device in the red circles occupy the USB bus”？
  • 0 in reply to Mickey Zhang
    TI__Guru 64326 points
    Mickey,

    If you have a USB 3.0 host that is connected to a USB 2.0 or 3.0 device their will be a "handshake" between the two to determine the data rate. If the device is a USB 3.0 device then the data rate will be 5 Gbps. However if the device connected occupies the bus intermittently the the overall data through will decrease even at the the data rate of 5 Gbps.

    When I said "each USB device in the red circles occupy the USB bus”, a device connected to the host must let the host know that it is ready to transfer information. Some devices blast information or occupy the bus more often than others but only one device can communicate on the bus at the same time even though multiple devices are connected to the bus. For more information look up "time-sharing" between USB devices.

    In addition there is overhead in the USB packets due to data encoding (8b/10b), time between packets, packet headers and other packet information that is not raw data. This decrease the theoretical limit for raw data around ~3.2Gbps