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TUSB211A: How long PCB routing can be supported after TUSB211A?

Feng Dong
Prodigy 80 points
Part Number: TUSB211A

Tool/software:

Our design will add the TUSB211A at 20 inch after USB Host，however，we want to know how long PCB routing can be supported after TUSB211A ? Assuming the use of FR4 PCB material。

Alternatively，how long PCB routing do you suggest adding TUSB211A after USB Host? Besides, how long PCB routing can supported after TUSB211A ? Assuming the use of FR4 PCB material.

  • 0
    TI__Mastermind 38735 points

    Hello,

    Feng Dong said:
    Our design will add the TUSB211A at 20 inch after USB Host，however，we want to know how long PCB routing can be supported after TUSB211A ? Assuming the use of FR4 PCB material。

    For this setup, I believe the TUSB211A would be able to support up to 5M of cable length/PCB routing on the post-channel. 20 inches is only about half a meter, and the TUSB211A can support up to 5M of cable length by itself, so I believe that 5M post-channel should be supported.

    Feng Dong said:
    Alternatively，how long PCB routing do you suggest adding TUSB211A after USB Host? Besides, how long PCB routing can supported after TUSB211A ? Assuming the use of FR4 PCB material.

    We recommend placing the TUSB211A as close as possible to an external connector, like a USB2 receptacle, that way the signal can look as good as possible before entering the cable.

    Please let me know if you have any other questions.

    Thanks,

    Ryan

  • 0 in reply to Ryan Kitto
    Prodigy 80 points

    Let me clarify, the design doesn't have connectors, so it wouldn't support external cable too. The design uses USB communication between devices on the PCB, but the USB signal traces is long than 50 inch on the PCB, so I will add a TUSB211A between the two devices, however, I don't know where is feasible。

    I knew the TUSB211A supported 5M of cable length, but I believed cable had less insertion loss than PCB trace（PCB trace is worse than cable）. So, I want to know how long PCB trace is supported after UUSB211A? Assuming the use of FR4 PCB material.

  • +1 in reply to Feng Dong
    TI__Mastermind 38735 points

    Hello,

    Typically for USB2/HS traces, due to the lower speed compared to USB3, we spec the amount of allowed cable length to be the same as the allowed PCB trace, I.E 5M of cable length is equal to 5M of PCB trace. However, it's also dependent on PCB design. If the signal is designed poorly or has reflections/noise in the signal, then the redriver would not be able to provide as much of a boost as compared to a clean PCB design.

    So for a USB2 design that is entirely on one board for communication between two device, with no connectors, a redriver should be able to support that setup, as our USB2 redrivers are typically spec'd to support up to 5M of cable length.

    Feng Dong said:
    so I will add a TUSB211A between the two devices, however, I don't know where is feasible。

    I would recommend placing it in the middle of the two devices, as placing it close to one of the devices could cause overcompensation potentially, due to the bi-directionality of the redriver.

    Please let me know if you have any questions.

    Thanks,

    Ryan