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TUSB1105 Output Status from Vreg(3.3)

HIDE66163
Intellectual 330 points
Other Parts Discussed in Thread: TUSB1106, TUSB1105

Hello,

I have a question about output status from Vreg(3.3) which is regulated supply voltage output.
On my hardware, output from Vreg(3.3) always stay in "High-z" irrespective of supply voltage to Vcc(I/O).
That means configration can't be dynamically changed between disable mode and normal mode.

I used in Internal Regulator Mode, and tested following steps;
Step1: Supply 5V to Vcc(5.0) (This 5V is powered from the Vbus line directly.)
Step2: Supply 3.3V to Vcc(I/O)
Output from Vreg(3.3) is in "High-z".  I confirmed output from Vreg(3.3) is in "High-z" on the step1, and it keeps same state on the step2.

Why output from Vreg(3.3) always stay in "High-z"?

Regards,
Hide

  • 0
    TI__Intellectual 1930 points

    Hide,

    Sorry for the delayed response. From your description of the problem, it sounds that it might either be a failed part or it could be the the device is in the incorrect mode due to something about the way it is connected.

    you could try replacing the part with a different unit and if the problem still persists, please send a schematic that we can review.

    Once again sorry about the extended delay to respond.

     

  • 0 in reply to Akhil Nair
    Intellectual 330 points

    Akhil,

    Thanks for the comment.

    After replacing the part,  I had confirmed it does not occur the problem.  It might be a failed part.

    Best Regards,

    Hide

  • 0 in reply to HIDE66163
    Intellectual 330 points

    Akhil,

    After that, I had received failure analysis report that the device was not a failed part...

    I'd like to make sure that the internal voltage regulator produces 3.3V in disable mode?

    (Disable Mode:  Vcc(I/O) is not connected, Vcc(5.0) is connected.)

     

    I'm still facing same problem that the internal voltage regulator produces <1V where Vcc=5.0V, Vcc(I/O)=2.5V.

    Best Regards,

    Hide

  • 0 in reply to HIDE66163
    TI__Intellectual 1930 points

    Hide,

    Am I understanding correctly that the you get the 3.3V output with certain pcs of the TUSB1106 and not with others?

    Between the NG and OK scope shots you have shown, is there any difference in the circuits?

    Regards,

    Akhil.

  • 0 in reply to Akhil Nair
    Intellectual 330 points

    Akhil,

    I checked Vreg voltage only on TUSB1105. (not on TUSB1106)

    On my verification, I get 3.3V Vreg output correctly on 84pcs, but 14pcs output below 1V in spite of connection both Vcc(5.0) and Vcc(I/O_2.5V).

    There is no difference in the circuit between NG and OK scope.

    On the NG parts, I get 3.3V Vreg voltage successfully on the first start-up.  However, it produces below 1V on the second start-up.  I can't understand why NG parts produce different Vreg voltage even though same circuit.

    My purpose is to make clear below;

    (1) Root Cause - Is this problem due to circuit?  Why this problem occur?

    (2) Find a Solution - Is there any solution not to occur this problem?

    Best regards,

    Hide

  • 0 in reply to HIDE66163
    Intellectual 330 points

    Akhil,

    Ishii-san who is FAE in TI Japan will send you an e-mail on this issue.

    Your cooperation is greatly appreciated.

    Best Regards,

    Hide

  • 0 in reply to HIDE66163
    TI__Genius 16510 points

    Closed via direct e-mail.

  • 0 in reply to DHarmon
    Prodigy 20 points

    Sorry to re-open an old thread, but I'm having exactly the same problem.

    Can someone please advise the contents of the direct e-mail?

    To reiterate, sometimes the 3V3 reg does not come up, even though the 5V is present (from the bus) and VCCio is connected to an on-board 3V3 rail.

    Pretty much wired up like figure 10 in the datasheet.

    This is happening to a subset of PCBs, and seems to be a recent phenomenon in a product that's been in production for a year or more.

    Cheers,

    Cam