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 issues

Other Parts Discussed in Thread: TXB0108

Hi,

I am using TXB0108, few things need to check with the expert here. VCCA is 1.8V and VCCB is 3.3V

1) Do I need to put any pull up resistor at both side data input?

2) I encounter some issue when I pull up (51kohm) both port A and B to relative VDD as initial stage, then manually touch the data to a low (ground), both input and output (VDDB data) will always LOW and will not recover. Why will this happen?

Need your advice. Thank you very much!

Best regards,

KH

  • KH - My feedback is below:

    Kum Hoo Lee said:

    1) Do I need to put any pull up resistor at both side data input?

    It is not necessary and not recommended. The Detailed Design Procedure of the datasheet specifies that pullups or pulldowns, if needed, must be greater than 50k.

    Kum Hoo Lee said:

    2) I encounter some issue when I pull up (51kohm) both port A and B to relative VDD as initial stage, then manually touch the data to a low (ground), both input and output (VDDB data) will always LOW and will not recover. Why will this happen?

    This is because the TXB family of translators requires the driver to source 2 mA in order to recognize a Logic High, and to sink 2 mA in order to recognize a Logic Low. This is covered in the Input Driver Requirements section of the datasheet.

    Disconnecting the short just leaves the external 51k pullup resistor to VDD. The current flow through that 51k pullup into the TXB0108 input pin is well below 2 mA, and so a Logic High is not recognized.

    Best Regards,
    Nirav