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SN74LVCH16T245-EP: Supply activation pulse is observed at the output

Furkan Fehmi Sefiloglu
Expert 3118 points
Part Number: SN74LVCH16T245-EP

Hi Team,

This is customer request can you please advise:

"

SN74LVCH16T245-EP level translator product of TI is being used in a design.

During tests, we detected a problem with this translator. VCCA and VCCB supplies are 3.3V and 5V respectively. Firstly, 5V supply is opened. ~30ms later, 3.3V supply is opened. At the point of 3.3V supply activation, a pulse is observed at the output pins of the translator. Duration of pulse is 150us, along this time the signal is high, then it falls to low. OE pin is grounded. DIR pin is pulled up, so the direction is from A to B.

What is the reason of this problem? Could you suggest any solution?

"

Thanks in advance

Best Regards

Furkan Sefiloglu

  • 0
    Guru 243220 points

    When the supply voltage is below the minimum specified in the recommended operating conditions, correct operation cannot be guaranteed.

    To disable the outputs during power up, ensure that OE is high.

  • 0
    TI__Guru* 96591 points

    Hi Furkan,

    When you say "opened" do you mean "Powered On" or the actual electrical meaning of "open" which is "Disconnected"?

    Also, can you provide a schematic and scope shots - as well as details of which pins the measurements are taken at?

  • 0 in reply to Emrys Maier
    TI__Expert 3118 points

    Hi Emrys

    Please find below feedback from the customer:

    "

    I think the first answer on the forum answered the question, and that was the reason I guessed.
    Answering to second reply yes "opened" means "powered on".
    I cannot share the schematic images, but I tried to elaborate on the question.
    This problem occurs during power up because the OE pin is directly connected to the ground.

    "

    Do you think we can confirm here if this is the reason?

    Thanks in advance

    Best Regards

    Furkan Sefiloglu

  • 0 in reply to Furkan Fehmi Sefiloglu
    TI__Guru* 96591 points

    Hi Furkan,

    Thanks for the clarification.  Yes, I'm sure that Clemens is correct - I had thought the same, but wanted to clarify the meaning of the terms used first, as one meaning would be the exact opposite of what I was initially thinking.