SN74LVC1G07: Absolute Maximum Ratings transient spec

1. There is no transient specification. The absolute maximum rating must not be exceeded, not even for a short time. But a clamping current of up to 50 mA is allowed, and if the IBIS model is to be believed, a current of 50 mA is reached only at output voltages below −1.05 V.

2. The SN74LVC1G07 itself simply connects to the output pin to GND, so it cannot generate voltages below GND. The undershoot is generated by the entire board, i.e., by the combination of the different impedances of the SN74LVC1G07's output, the trace, and the receiving device's input. To prevent reflections, the trace must be properly terminated. Try source termination, i.e., adding a 33 Ω series resistor directly at the output pin.

No, footnote (2) allows you to exceed the voltage limit in this case.

There is a plain silicon diode from GND to the pin. For voltages above −0.5 V, no noticeable current flows.

The IBIS model is not the datasheet, so the diode's forward voltage characteristics are not actually guaranteed.