• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 21 subscribers
  • Views 645 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74LVC2T45: Input transition (rise and fall)

user4823495
Prodigy 60 points
Part Number: SN74LVC2T45

Hi team

We have an older design where SN74LVC2T45 has been used as a bus tranceiver/level translator. The problem is that the rise/fall time is rather slow. Close to 1us worst case.

I have read SLLA364A and understand the issue.

We have seen oscillations but we can live with that. The current consumption does not increase very much when the input changes with 200 kHz with rise/fall time of 1 us.

How harmfull is this to the device? According to SLLA364A  it is harmfull due to increased current consumption but is really a big problem?

It would be nice just to add a schmitt trigger, but we cannot really do that when the line is bidirectional? And we cannot find any bidirectional level translators with true schmitt trigger input.

I hope you have some sort of a suggestion as I cannot think of anything.

BR Henrik

  • 0
    Guru 317450 points

    The internal circuits are not designed to oscillate or to handle large currents; damage certainly could occur (see Implications of Slow or Floating CMOS Inputs (SCBA004)).

    You already have a DIR signal, so you could add a three-state buffer/switch (-125 or -66) to disconnect the output of the wrong Schmitt-trigger buffer.
    There is no device that combines a Schmitt-trigger input with a three-state output, except the -99.