We want to use TXB0304 to transfer 30Mhz CLK from 3V3 to 1V8. Owing to the trace at the output is too long(about 7000mil) , we found a waveform with poor quality. What confuses us is the first undershoot on low to high(mark with red). We doubt that the one-shot function was closed at this moment, but Turn-On duration is up to 10ns  mentioned in the databook.

I have questions about TXB0304 this part, especially on one shot circuits. 

1、What causes the first undershoot on low to high(mark with red)

2、TXB0104 Application mention that   “ The O.S.circuits turn on the PMOS transistor (T1) for approximately 10 ns or 95% of the output edge, whichever occurs first.”，Is this TXB0304 the same?

3、How to test  the opening and closing time of one-shot.(Connect a 1K resistor in parallel to ground？)

Thanks