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SN65LVPE502B - power-on order for USB host, VBUS, redriver and USB device

msmn
Intellectual 805 points

My customer asked me power-on oder for USB host, VBUS, SN65LVPE502B and USB device.

The customer tried some power-on sequence as below.

a) Simultaneously power on USB host, SN65LVPE502B and USB device

b) First power on USB host and then power-on USB device and SN65LVPE502B simultaneously.

c) First power on USB host, second  SN65LVPE502B, last USB devic.

And so on ...

They sometimes saw some interoperability issues. So they would like know what power-on order is the best.

Could you tell me the best power-on order including VBUS ON timing?

Regards

Saito

  • 0
    TI__Guru* 76130 points

    Hello Saito-san,

    We need more information in order to tell you the best sequence.

    Are you using VBUS to power all the devices?(Host, Re-driver and Device)

    Can you share your schematic?

    Can you elaborate more about these interoperability issues?

    Regards.

  • 0 in reply to Elias Villegas M.
    Intellectual 805 points

    ELIAS-san,

    > Are you using VBUS to power all the devices?(Host, Re-driver and Device)

    No. All devices are not powered from VBUS. Each device has an independent power source.

    The customer used the following configuration 1) when they saw this issue.

    1) USB host <-- usb cable --> Redriver <-- usb cable --> USB device (self powered device)

    The customer WILL use the following configuration 2) when they release their product to market.

    2) USB host + Redriver <-- usb cable --> USB device (self powered deivce)

    They will develop a system with a USB host and a redriver.

    The self-powered USB device which they will use was developed by an unknown vendor.

    > Can you share your schematic?

    I don't have a schematic.

    > Can you elaborate more about these interoperability issues?

    They say that the USB host might have detected the physical connection to the USB device and an unexpected behavior might have happened after the connection. But they say that they are not sure whether this is a reliable information. 

    I think that the following power sequence would be good for any configuration.

    c) First power on USB host, second  SN65LVPE502B, last USB device.

    Please let me know your comment.

    Regards

    Masumi Saito

  • 0 in reply to msmn
    TI__Mastermind 36085 points

    Hello Saito-san,

       your assumption is correct, a normal power sequence is first power on USB host, second  SN65LVPE502B, last USB device. I would like to know if they have the device attached to the re-driver all the time or they are connecting/disconnecting it during the issues.

    best regards,

    Diego.

  • 0 in reply to Diego Cortes
    Intellectual 805 points

    Diego-san,

    Thank you for your response.

    > I would like to know if they have the device attached to the re-driver all the time or they are connecting/disconnecting it during the issues.

    I think it's important to know it. I'll tell you when I get the information from the customer.

    I would like to ask one more about the power sequence. What timing is the best for the USB host to generate VBUS?

    c) First power on USB host, second  SN65LVPE502B and the USB host generates VBUS and then last USB device.

    I think it's ideal. What do you think?

    Regards

    Saito