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USB3 redriver issue using SN65LVPE502

Other Parts Discussed in Thread: SN65LVPE502, SN65LVPE502CP

I am working with a customer who is using this part as a redriver in a USB3 cabling system.

I read in the datasheet that the part will enter a sleep mode when no traffic is detected on the input. What is the exact mechanism for doing this? How long does it take to wake up? Is it possible to disable this feature?

 

Thanks,

John

  • Hello John,

    the exit time from sleep mode is 100us max.

    Can you tell me where exactly did you see the "traffic" note.

    Regards.

  • On page 1 of the spec in the description of Low Power Modes, I found the following information.

     

    RX Detect Mode – When no remote device is connected

    Anytime SN65LVPE502 detects a break in link (i.e., when upstream device is disconnected) or after powerup fails to find a remote device, SN65LVPE502 goes to Rx Detect mode and conserves power by shutting down majority of the internal circuitry. In this mode, input termination for both channels are driven to Hi-Z. In Rx Detect mode device power is <10mW(TYP) or less than 5% of its normal operating power This feature is useful in saving system power in mobile applications like notebook PC where battery life is critical.

     

    The chip is wired such that it will enter Rx Detect Mode during operation. How long does it take to exit Rx Detect Mode? Is it also 100us?

     

    John

     

     

  •  A USB 3.0 device shall exit from RX.Detect and transition to Polling upon detection of a far-end low-impedance receiver termination RRX-DC as defined in the USB 3.0 Specification.

    If  no far-end termination is detected, then the device shall enter to a subsatate (RX.Detect.Quiet) and wait 12ms before looking again for a far-end termination, after 8 attempts of no detecting a far-end termination (80ms aprox.)the device will drop to USB 2.0

    Regards.

  • Can you provide more details on how the receiver end of the re-driver chip operates? My understanding is the redriver chip basically "amplifies" the USB signal and reconditions it. The redriver does not receive USB packets and then resend them. Instead, it just passes the USB traffic through the part. Is my understanding correct?

    In my application, the USB host will stop transmitting data at various times. It may stop for many minutes before enabling it's transmitter and sending data. What I am observing is that none of the data makes it through the redriver circuit. I suspect the redriver is in a low power state of some sort. Does this sound plausible. If so, how to get the redriver to operate under these conditions?

     

    John

  • John,

    Can you provide your schematics for review?

    Regards.

  • I am using the SN65LVPE502CP Evaluation Board. I have attached the schematics for that board.

     

     

    http://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-components-files/138/2703.SN65LVPE502CP_5F00_EVM_5F00_Schem.pdf

  • I would like to answer my original question in a different manner.

    If I drive a PRBS-7 pattern into the SN65LVPE502 part, will it receive the pattern and re-transmit it? If the pattern turns off for a long time and is then turned back on, what is the part's behavior?

    Are there limitations in the type of patterns that I can transmit through the SN65LVPE502?

     

    Regards,

    John

     

  • Hello John,

    I'd like to take one of your previous posts first.

    Does your system works normally at the beginning and then after the host is idle for a period of time the re-driver stop working?

    Are you plugging-in VBUS powered devices to the re-driver?

    What I'm trying to discriminate is if your problem is related to the Errata #1 for this device, please go to the below link.

    Also, make sure you are not populating JMP7 and JMP8.

    http://www.ti.com/lit/er/sllz070/sllz070.pdf

    Regards.

  • Elias,

    My system has some Intellectual Property and I do not feel comfortable providing additional information on a public forum. Is there a private communication channel (i.e. email or phone) that we can use to continue this discussion?

     

    Regards,

    John

  • Sure,

    You can email me to elias.villegas@ti.com

    Regards