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tusb522p: Cascaded USB redriver parts

Bruce Dove
Prodigy 60 points
Part Number: TUSB522P
Other Parts Discussed in Thread: SN65LVPE512, , TUSB8044

Hi,

If we have applications that may place two USB3.0 gen1 (5Gbit/sec) redtriver parts in series, because of high loss, will this work? We have both the TUSB522 parts as well as the SN65LVPE512 parts in designs. Will the USB3.0  jitter requirements still be met? Would there be other SI effects to worry about? We would need to consider cases with two TUSB522 parts in series, a TUSB522 in series with a SN65LVPE512, and two SN65LVPE512 parts in series. Realize that the SN65 part is not recommended, however, we have some systems built with this part.

In situations with high USB line losses, is it a good idea to place a hub part downstream from the host in an effort to "retime" the USB channel, possibly also putting redriver parts on both sides of the hub?

Thank you,

Bruce

  • 0
    TI__Mastermind 23815 points
    Hi Bruce,

    LVPE502 and LVPE512 are not recommended for new designs, they were replaced by TUSB522P.
    Placing LVPE512 and LVPE502 in series will result in interoperability issues.
    You can place TUSB522P in series.
    We haven't tested the combination between TUSB522P and LVPE502/512(NRND).

    Besides the channel attenuation and bandwidth limitations, jitter, skew, noise, x-talk can affect the signals.

    You can place a HUB like TUSB8044, it will be bigger, consume more current and every HUB will make a new level in USB hierarchy, while the redrivers are smaller, consume less power and are transparent in the USB hierarchy.

    Regards
  • 0 in reply to Moises Garcia
    Prodigy 60 points

    Sorry could not reply sooner. Had other issues.

    We understand that the hubs are larger and consume more power. Those we can accommodate. Also the latency is not a problem for us. The problem we want to overcome is the losses in long USB paths, and the uncertainties with the redrivers. We have concerns with cascading redrivers; we do not control what gets plugged into the port, and wish to be fully compliant there so any device can be plugged into it.

    The hub part datasheet do not state any of the analog capabilities for the hub parts, for receive or transmit. Yet they do seem to offer the ability to regenerate the USB link. That is valuable in our application. 

    What downstream port loss capabilities do the hub parts offer? Can they support a full 20db loss on the downstream port? If not, what channel loss can be tolerated by the hub parts? We assume that this is at least 12dB, since the target device is permitted 2.5 dB and also permit a full length of USB3 cable, which would provide another 10dB.

    Do any of the hub parts offer any program control features for downstream analog port parameters, ie for EQ and drive?

    Thanks,

    Bruce

  • 0 in reply to Bruce Dove
    TI__Mastermind 23815 points
    Hi Bruce,

    The TUSB8044 has no features to control EQ, DE, or OS; however, the HUBS go through interoperability testing where 5 hubs are chained with 3m USB3 cables, passed the test without any problem.

    Regards