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Confirm the description of c5535 datasheet

Kaka
Guru 24520 points

Hi community member,

I have a question about the description in datasheet.

The datasheet of C5535 is described it as below.

-----------------------------------------------------------------------------------------------
> 6.3.1 Power-Supply Sequencing
>
> Note: If the device is powered up with the USB cable connected to
> an active USB host and the USB PHY (USB_VDDA3P3) is powered up
> before the USB Core (USB_VDD1P3, USB_VDDA1P3), the USB Core must
> be powered within 100 ms after the USB host detects the device has
> been attached.
-----------------------------------------------------------------------------------------------

I do not understand that "the USB host detects the device has been attached".

Which the timing does this description pointed out?
1) USB_DP will be Pull-up.
2) The voltage of USB_VBUS will be exceeded the threshold of settings values in host.
3) Others case.

If other case, would you please explain the timing?

If you have any questions, please let me know.

Best regards.

  • 0
    TI__Expert 7470 points

    Hi,

    This comes from the USB 2.0 spec which requires enumeration to be complete within 100ms from when the host detects a device.

    With respect to the statement, you could have the USB PHY powered before powering the USB core. In this condition, if you have the USB cable attached to a host, the host will detect the C5535 USB device. But from this point, the C5535 should complete the enumeration process within 100 ms otherwise the USB host will not recognize the device.

    So, the description should actually say that the USB Core power has to be applied, C5535 should complete USB configuration and enumerate with the USB host within 100 ms after the USB host detects the device has been attached.

    Hope this clears the issue.

    Regards,

    Sunil Kamath

  • 0 in reply to Sunil Kamath
    Guru 24520 points

    Hi,

    Thank you for reply to me.
    Please let me confirm my understanding just in case.

    This description is showed that if the device need to meet the standard of USB 2.0, other power domains should be powered up within 100ms from when the host detects a device.
    Is this correct at this time?


    Also, I do not understand what is the factor in case of "when host detect a device".
    [Question]
    What is the source that determine the device has been connected by the host?
    1) USB_DP will be Pull-up/Pull-down at device(i.e. Response from device)
    2) The voltage of USB_VBUS will be exceeded the threshold of settings values in host.
    3) Others source
        * If other sources, would you please explain about the source?

    Best regards.

  • 0 in reply to Kaka
    TI__Expert 7470 points

    Hi,

    Yes, your understanding is correct. I would only like to correct my earlier comment - the actual enumeration (what kind of USB device - MSC, ISO etc) happens later in the process.

    The host detects that a device is connected on USB_DP (or USB_DM in low-speed case) Pull-up by the device PHY.

    Regards,

    Sunil Kamath