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Isolated USB Hub with TUSB2036 and ADuM4160

Frank-Christian Kruegel
Prodigy 60 points
Other Parts Discussed in Thread: TUSB2036

Dear Sirs,

I'm building an isolated USB hub with the TI TUSB2036 and the AD
ADuM4160, which isolates the upstream port.

Problem: The hub isn't recognized. When removing the ADuM4160 and
connecting the upstream port directly the hub is enumerated. This
shows me that the basic hub circuitry is working. Clock, Reset and
voltages are correct.

The AD isolator chip is supposed to be transparent to the USB
protocol. The 1k5 pullup on DP0 is integrated into the isolator chip
and controlled through pin 12 (PIN, high=pullup active), so it is not
drawn in the schematics. I failed to find a suitable alternative to
the AD chip from TI.

Any suggestions? I'm completely open to alternative chip solutions.

Regards Frank

 

  • 0
    TI__Guru* 76130 points

    Hello,

    I think your problem is the connection of ADUM's PIN terminal, it should be connected to 3.3V and remove the R105. Also, the terminal DP0 of the hub should be connected as well to DP0PUR.  DP0PUR should not be connected to PIN, since it is already internally connected in the hub.

    Regards.

  • 0 in reply to Elias Villegas M.
    Prodigy 60 points

    Problem solved. The ADuM does not replace the 1k5 pullup. PIN only controls whether a detected pull-up is signalled to the other side.

    Thanks for your input.

     

  • 0 in reply to Frank-Christian Kruegel
    Intellectual 290 points
    Hello
    Is ADuM3160 compatible with USB-OTG?
  • 0 in reply to aseok tag
    Genius 4680 points

    aseok tag said:
    Is ADuM3160 compatible with USB-OTG?

    The official announcement from Analog Devices tells,

    ADuM3160 FAQ Section - Analog Devices Wiki
    wiki.analog.com/.../adum3160

    Q6: Can ADUM4160(/3160) support OTG (On The Go) USB?
    The ADuM4160 does not support On The Go. This part of the USB specification has modes where power is not present on the cable, and we can not pass signals to initiate communication if power is not present. We recommend dedicated host and peripheral ports if isolation is required.


    Not just for the power absence on OTG, ADUM3160 has another reason incompatible to OTG
    - The role (host/device) of each side of ADUM3160 is fixed by internal circuitry.

    Usually, the isolation of OTG is done at the ULPI interface.

    Tsuneo

  • 0 in reply to Tsuneo Chinzei
    Intellectual 290 points
    Would you please give me a description of PDEN and PIN pins of ADuM3160 and their possible configurations?
    I have read the datasheet but i need for explanation.
  • 0 in reply to aseok tag
    Genius 4680 points

    aseok tag said:
    Would you please give me a description of PDEN and PIN pins of ADuM3160 and their possible configurations?

    As of the background,

    USB D+/D- lines are pulled down at host side, pulled up at device side.

    7.1.5.1 Low-/Full-speed Device Speed Identification (usb_20.pdf)



    ADuM3160 has on-chip resistors for these pull-up/pull-down.

    PDEN: Pull-Down Enable
    Both of D+/D- lines are pulled down by 15k Ohm resistors at device-facing side of ADuM3160. Always enabled in normal operation: this pin is just for test purpose.

    PIN: Upstream Pull-Up Enable
    D+ or D- line, according to SPU pin, is pull-ed up by 1.5k Ohm resistor at host-facing side of ADuM3160. Usually enabled in normal operation. Device may control this pin,
    a) to delay enumeration at plug-in
    or
    b) soft-detach / soft-attach for re-enumeration (for example, on boot-loader)

    Tsuneo