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tusb8041-q1 regarding USB 2.0 connection, automotive grade, reference design usage, device driver

Niranjan Madhavan
Intellectual 605 points
Other Parts Discussed in Thread: TUSB8041-Q1

Hi 

I am in an early stage of designing a USB 3.0 hub. I was thinking of using tusb8041-q1 automotive grade for design as my product have a fair share of automotive market. I have couple of qustions

1. What is this automotive grade different from the catalog grade? I am seeing there is a package difference and price?
2. Can I use the same reference design as shown in url: http://www.ti.com/tool/tida-00288  

3. My hub would be connect to a host pc with USB 3.0 port. But the downstream ports would be two usb 3.0 device and two usb 2.0 device(as shown in attachment). Data rate is very critical in my application. I want 5GbPS from USB 3.0 devices and 480mbps from USB2 devices simultaneously. In other-wards, the plugging in of usb 2.0 devices should not downgrade the hub performance to usb 2.0. Is it possible? 

  • 0
    TI__Guru* 76130 points

    Hello,

    1. There are several process that the device has to go through in order to e automotive grade, however, from an end-user point of view the only changes would be the package, voltage ranges and operation temperature.

    2. Yes, you can use that reference design.

    3. The hub does not manages the bandwidth, the available bandwidth is managed by the operating system. The 5Gbps is the maximum data rate, but it is not the actual data throughput, the USB protocol add several layers of overhead data, so when you are sending a 8-bit word, the USB protocol is actually sending a package of more than 20-bits, the same happens with USB2.0

    Regards

  • 0 in reply to Elias Villegas M.
    Intellectual 605 points

    Thank you for the replies

    Sorry, I think I did not frame the third question properly, Lemme try again!

    Ignore the values 5Gbps /480 Mbps and consider operating system is giving me the maximum performance, and the host PC has usb 3.0 bus capability.

    In a very high level overview, I am connecting two USB 3.0 Devices to the hub at downstream and not using the other two ports initially. And I am getting a data rate of X mbps. Then after some time, I am connecting usb 2.0 devices to the two vacant ports. Nothing is changing in terms of operating system, host PC hardware etc. So what will be the new data rate between the host PC and USB 3.0 devices? Would it be X mbps itself or it will downgrade to a USB 2.0 data rate of (X-k) data rate. The reason I am asking is, I heard that in a USB2.0 hub, if we connect USB 1.1 device, the whole system will downgrade it to a USB 1.1 hub(reduced performance). If the same scenario is  applicable to USB 3.0, I should be aware of that. 

    Basically would USB 2.0 traffic affect usb 3.0 when connected parallel is  my question?

  • 0 in reply to Niranjan Madhavan
    TI__Guru* 76130 points
    Hello,

    USB3.0 and USB2.0 are actually two physically separated interfaces, so the Hub and the Host are going to be working in parallel with the USB3.0 and USB2.0 devices.

    Your USB3.0 devices will remain connected at SuperSpeed no matter that you also have USB1.1 devices connected to the Hub.

    Regards
  • 0 in reply to Elias Villegas M.
    Intellectual 605 points
    Thank you. Thats all I need. Sorry, if I bothered you with some very basic question. I was almost sure about that, but just double check ( I am still a conservative junior level person!) Still curious, how they will automatically switch the core according to the device! I think I will learn as a process of this project. Thanks again.