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TUSB2077A Debugging Help

kailas narendran
Prodigy 20 points
Other Parts Discussed in Thread: TUSB2077A

I'm having some trouble getting the TUSB2077A hub to work.

My schematic is shown below.  It's a close copy of the reference diagram from p13 of the datasheet.  This is to be used in an "installed once" setup, so I don't need power management for the ports of the hub.  There are a few additional differences that I don't think would cause the behavior I'm seeing (described below)

When I power up the circuit, I'm able to confirm:

- The clock oscillates at 6MHZ

- There is 3.3v on all power pins

- reset is high

All that being the case, when I plug it into my host computer, nothing happens (windows doesn't indicate it's detected a new device, the hub I connect it to doesn't illuminate to indicate the device has been enumerated, etc.)

Any thoughts as to what could be going or where to start with debugging?  The chip is a bit of a black box and i'm not sure what signals I can probe to deduce what could be happening.

Thanks!

-kailas

  • 0
    TI__Guru* 76130 points

    Hello Kailas,

    Tie all the /OVERCUR# terminals to 3.3-V through a 10K resistor.

    Make sure you active low Reset signal has a duration between 1ms and 3ms on power-up and that the clock source for the hub is stable before the Reset is de-asserted.

    Add the passive components on DP and DM lines as shown below.

    After you connect the hub to your host, are the clock and Vcc lines still stable?

    Regards.

  • 0 in reply to Elias Villegas M.
    Prodigy 20 points

    OK, I totally missed that I need to tie /OVERCURX high, my bad.  Would that result in the part not getting enumerated?  Will do that and let you know what happens.

    After I connect my host Clock and VCC look fine.

    -k