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USB-REDRIVER-EVM: EFFECT OF THE REDRIVER CARD ON DATA TRANSFER

FURKAN DURAN
Prodigy 115 points
Part Number: USB-REDRIVER-EVM
Other Parts Discussed in Thread: TUSB501, TUSB211, TUSB522P

Hi,

We want to transfer data over the camera with a USB 3.0 cable at a speed of 5 Gbps. For this, we made a PCB design based on the USB-REDRIVER application suggested by Texas Instrument. Also, we didn’t  observe a REDRIVER effect with the PCB board we made in the cases I mentioned in the appendix. For this, we tried some of the mods on the card's datasheet. But the REDRIVER card doesn’t work as we want. When we increased the USB 3.0 cable length, we observed that the fps value of the camera decreased. Also, when we put a REDRIVER between every 2 meters of cable, we could not see the REDRIVER effect we wanted.

 I would like you to explain the effects of the modes specified in the REDRIVER card and support the test setup of the card.

NOTE: REDRIVER card supplies are provided with a DC power supply. There is no design error in the designed PCB.

Best Regards

Furkan


  • 0
    TI__Guru 64326 points

    Hi,

    It is probably best to look at the eye diagrams for your USB 3 interface here to understand the signal integrity of your system. It would be helpful to understand the output of the camera, state 1 and state 2. What is the decrease in performance that you see (in fps)? 

  • 0 in reply to Malik Barton57
    Prodigy 115 points

    Hi,

    Our system works smoothly for case-1. There is no fps reduction for Case-1. But in case-2, since the USB3.0 cable length increases, there is a decrease of approximately 7 fps in the camera we use.On the REDRIVER card, do the mods we use have any effect on fps drop?

    Best Regards

    Furkan

  • 0 in reply to FURKAN DURAN
    TI__Guru 64326 points

    Hi Furkan,

    Since you are using TUSB501 only the output de-emphasis and swing will help to compensate for loss in longer and longer cables and these settings remained unchanged. in your test cases case 1 vs case 2. It is important to understand the signal integrity through direct measurement as this may be a issue of jitter rather than overall insertion loss. Also you have TUSB501 device on both USB 3 RX and TX correct? Have you tired different 4 meter USB3 cables? Some cables can perform better than others (lower losses). 

  • 0 in reply to Malik Barton57
    Prodigy 115 points

    Hi Malik,

     

    We use TUSB501 for USB 3.0 Tx and Rx lines of our system, TUSB211 for USB 2.0 Tx and Rx line. We tried different 4 meter USB 3.0 cables but didn't get the result we wanted.

     

    Best Regards,

    Furkan

  • 0 in reply to FURKAN DURAN
    TI__Guru 64326 points

    Hi Furkan,

    I see if you could provide some eye diagrams that would help me to understand the signal integrity of your system. It will be easiest to measure in the direction from the PC towards camera. Let me know if you have any questions here. Since you have redrivers on both TX and RX, have you tired changing the settings between the two redrivers? Camera USB3 TX may require different settings that PC USB 3 TX. In your PCB design  are the trace length of the pre and post channel for both TUSB501 symmetrical? 

  • 0 in reply to Malik Barton57
    Prodigy 115 points

    Hi Malik,

    The path lengths before and after the TUSB501 chip are not symmetrical in design. In addition, we changed the individual modes of both the TUSB501 on the TX side and the TUSB501 chip on the RX side, and we tried all of these modes between the PC-Camera. But the system did not work the way we wanted. In addition, there are things I want to ask;

    1-) Do I have to change the modes of the redriver chips when I change the PC and camera in my application?

    2-) Should we constantly change the modes of the Redriver chips according to the main user?

    3-) Does Texas Instrument have any suggestions about the applications of the mods in the Redriver chips?
    Note: Schematic and PCB drawings are attached.

    Best,

    FurkanUSB30_Redriver_Hub_Test.zip

  • 0 in reply to FURKAN DURAN
    TI__Guru 64326 points

    Hi Furkan,

    Sorry for the delay here. Had some trouble opening your Altium project on my side. Are you seeing the performance drop with both boards (ESD+CMC vs None)?  It is still important to understand the signal integrity through direct measurement as this may be a issue of jitter rather than overall insertion loss.

    1)  You should not need to change the redriver settings for every combination of PC and camera however PC and camera performance can vary and may require changes to get he desired performance.

    2) I recommend running the USB 3 TX compliance test and find settings that allow this test to pass in your test setup. This will ensure your setup has compliant signal integrity. 

    3) Schematic and layout look good. I would suggest to keep both redrivers on the bottom layer to avoid unnecessary vias. What is the trace impedance in your design? Changing the redriver settings will only help to compensate for Insertion loss in your system. Such a drop in performance maybe caused by excess jitter in 4m cable case (and case 4). TUSB501 will not be able to compensate for jitter here. 

  • 0 in reply to Malik Barton57
    Prodigy 115 points

    Hi Malik,

    Both cards have poor performance(Protected, Unprotected). But But we did our tests on the unprotected one. We tested the performance of the cards by way of USB test software on the internet, but we couldn't obtain the parameters we wanted in the test results. Therefore, we test our REDRIVER cards between camera and pc. Is there a USB3.0 and USB 2.0 test software you can recommend to us here?

    In addition, we have rohde & schwarz hm03004 in this brand model, an oscilloscope and a TRVNA 1300 with a value of 1.3Ghz. What kind of test setup would you recommend us to set up with these?

    We tried many different combination options that you mentioned in item 1, but the result was negative in all of them, and even in some combinations the fps of the camera was 12 fps to 5 fps, we observed that it fell. (For State-2)

    What range should the jitter be and what do you suggest we do when the jitter value exceeds a threshold?

    As seen in the attached picture, the path impedance is 90 ohms.

    Finally, if we use TUSB522P instead of the TUSB501 we currently use, are there any possibility of encountering the same problems?

    Best regards,

    Furkan

  • 0 in reply to FURKAN DURAN
    TI__Guru 64326 points

    Hi Furkan,

    For testing USB 3.0 and USB 2.0 compliance you will need to use the USB xHSETT provided by the USB-IF to put USB Host or Devices into compliance mode. Software packages included with high speed scopes are used to measure the USB compliance patterns, collect data and generate the desired compliance reports. This type of software is provided from the scope manufacture, companies like Lecroy or Keysight.

    Unfortunately your scope will not be able to adequately measure the USB compliance patterns. To measure eye diagrams you will need a high bandwidth scope, I recommend bandwidth greater than 12 GHz for USB 3 Gen 1 test or lower.

    Jitter limits for USB 3 Gen 1 are specified by USB 3 specification and can be found in Table 6-20. Normative Transmitter Eye Mask at Test Point TP4.

    If the problem here really is jitter then there is not much a redriver can do to compensate however we should evaluate the measured eye diagram to confirm this. Could you elaborate on the performance at lower EQ/DE settings? I am curious if you see a significant drop in performance. In some cases over equalization can also cause issue with performance (i.e. eye mask violations). 

    TUSB522P does have some improved performance over TUSB501 but redrivers cannot compensate for jitter, only can re-timers. We should work to understand what the signals look like with your 4m cable to find a proper solution.