TXB0104: If we have no GPIO to control OE, is there any other method about it?

Hi Luck,

1. Could we use 1.8V to realize RC delay for giving OE Pin since the design has no more GPIO to control it?

I would recommend against applying a slow input directly the the OE pin of the TXB0104, my reasons are explained in this application report: Implications of Slow or Floating CMOS Inputs

You can, however, add a delay circuit to hold the OE pin low during startup:

The Schmitt-trigger buffer can safely support slow inputs, and will output a clean square signal to the TXB0104's input when the capacitor charges to a high enough value.  The RC circuit can be adjusted to have different amounts of delay depending on your system needs.

2. If we draw the PCB line of TXB0104 is about 700cm, is there any problem about the PCB?

700 cm is incredibly long for a PCB trace (7 meters?! What kind of PCB is this?).  I would expect the capacitance on the line to be overwhelming to the device.  We recommend maintaining less than 70 pF on the line.

It sounds like you need something like a high power line driver rather than a translator.