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.

TXB0108: Logic forum

Part Number: TXB0108
Other Parts Discussed in Thread: LSF0108

Hi,

We have been TXB0108PWR bidirectional level translator in one of our design, the PDF file for the scheamtics is attached.

for ex. : the GPIO6_3P3 and GPIO7_3P3 are shorted and  GPIO6 is set as input and GPIO7 is set as output, then the input GPIO6 is not able to track the changes in the GPIO7 output GPIO, the voltage at the shorted point is 1.6V.

so my doubt is, if the GPIO6 has a pull pu resistor of 4.7k to 1.8V, in this case the bidirectional buffer will give the output as 3.3V on the GPIO6_3P3 net.

and when GPIO7 is low the GPIO7_3P3 will be 0V.

so when i connect these two GPIO6_3P3 and GPIO7_3P3 lines what will happen?

will the auto direction detect properly which line is input and which is output, or will it cause a problem?

is there any possible solution to this problem?

Thanks,

R.Rohith yadav

TXB0108PWR CIRCUIT.pdf

  • Hi Rohith,

    I am confused as to why this configuration is done.
    There will be bus contention where one input is trying to drive the output high while the other side is trying to be low.
    TXB family of devices is not recommended to be connected to external pullup resistors since they have internal 4K series resistors which forms a voltage divider.
    The TXB device also requires the input host to have enough drive strength to overdrive the previous state. The loopback configuration here may not have this capability.
    For more information, please refer to the app note:
    www.tij.co.jp/.../scea060.pdf
  • Hi Shreyas,

    can we use TXS0108 series of the level translators for this application, as that does not have any series resistor and is applicable for both opendrain and push-pull applications.

    or do you recommend any other compoent with the same footprint?

    Thanks,

    R.Rohith yadav

  • Hi Rohith,

    I couldnt understand the requirement or the question here.

    TXS0108 can be used and can have shorted B ports together. The A6,A7 ports will try to be at the same level. TXS have internal pullup resistors so 4.7K external resistors are not required.

  • Hi Shreyas,
    The GPIOs in the scheamtics are in the push-pull configuration, but the processor has some internal pull-up and pull-down resistor, so when we use these GPIO it causes the problem.
    so do you recommend any other solution or any other level translator for this application?

    Thnaks,
    R.Rohith yadav
  • Rohith,

    In that case, both TXB or TXS is not recommended.

    consider the LSF0108 as auto bidirectional translator device option. It needs external pullup resistors to achieve translation.