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TXB0108: input sequence

ACGUY
Guru 11170 points
Part Number: TXB0108

Hello E2E,

I have issue about TXB0108 on our customer board.
  :  When Vcca is 1.8V and VccB is 3.3V, OE is Low at initial state.
  :  24-MHz clock input to 1.8V side.
  :  OE to be High.
  :  3.3V side is not output nomally.

I think that this device should not be inputed before OE is set to High.
Is it correct?

Regards,
ACGUY

  • 0
    TI__Guru 61870 points

    Agguy,

    would you please send schematic and the waveforms.
    I want to understand more about the' 3.3V side is not output normal' statement.

    what is the parasitic load cap and the probe cap when measured on the scope?

    TXB is sensitive about the loading cap and have layout restrictions on the output trace length.

  • 0 in reply to ShreyasRao
    Guru 11170 points
    Shreyas,

    I do like to change the question.
    When 24-MHz clock is input to 1.8 V side within 1 usec from OE-High-edge, is this device capable of normal operation?

    Regards,
    ACGUY
  • 0 in reply to ACGUY
    TI__Guru 61870 points
    ACGuy,

    Referring to the switching characteristics on page 8 of the datasheet, the enable time max for 1.8V operation is 1us( time from OE asserted to A/B) and hence I would say that the normal operation is not guaranteed when input is <1uS from OE edge.