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TXS0108E: TXS0108 problem with long line.

Frank Xiao
Genius 12055 points
Part Number: TXS0108E
Other Parts Discussed in Thread: SN74LVC8T245

Hi team,

My customer is using the TXS0108E now. schematic is below, MCU control A pin, B pin to LED.When the line is too long, the signal will oscillate, the LED will have some problems. Could you please help analyse the reason of the problem?

3443468773

  • 0
    TI__Guru* 96862 points
    Hi Frank,
    I have asked our translation expert to take a look at this and get back to you. He will respond within 24 hours.
  • 0
    TI__Guru 58990 points
    Hi Frank,

    Please share the full schematic if possible. Are there pullup and or pulldown resistors on the lines? What is the trace line length and is it possible to place the device close to the receiver?

    The TXS is not able to drive LEDs due to the low drive strength and the overall architecture of the TXS.
    Would you consider using the SN74LVC8T245 instead?
  • 0 in reply to ShreyasRao
    TI__Genius 12055 points

    Hi Rao,

    The LED  board integrated the 245. So the driver ability is fine. But they didn't use the pull up resistors.

    The line length is 40cm, cannot be improved.

    Could you please help analyse the reason of the problem? 

    Thanks.

  • 0 in reply to Frank Xiao
    TI__Guru 58990 points

    Hi Frank,

    This is the snip from the Guide to TXS app note, where it is mentioned about the loading on the TXS to be kept to a minimum. The one shot which could be triggered by the reflection of the signal and hence to keep the trace length short. Do you have the full schematic and the scopshot of the signal? what is the datarate and the cap loading? The 100ohm series resistors can be changed to different values ( 25,50,150ohm) to see if the reflection can be dampened.

  • 0 in reply to ShreyasRao
    TI__Genius 12055 points

    Hi Rao.

    Do you have some recommendation to solve the problem? For example, SN74LVC8T245. Thanks.

  • 0 in reply to Frank Xiao
    TI__Guru 58990 points

    Hi Frank,

    As i had replied in the first post, I would recommend SN74LVC8T245 for driving long lines/ parasitic cap loading/ driving LEDs.

    Please let me know if the customer can consider using this and if it resolves the issue.