PCA9306: SVO diode

The PCA9306 does not have a static voltage offset. It does not buffer the signals; it is a passive switch.

The internal circuit is explained in the application note Voltage-Level Translation With the LSF Family, and in [FAQ] How do the LSF translators work?

This device is perfectly symmetrical. It does not matter whether VREF1 or VREF2 has the higher voltage, but the EN connection and the 200 kΩ resistor must be on the high-voltage side.

Thanks a lot